diff --git a/Two-phase-Two-phase/one-patch/mesh_study/R-one-patch-mesh-study-alternative.py b/Two-phase-Two-phase/one-patch/mesh_study/R-one-patch-mesh-study-alternative.py
new file mode 100755
index 0000000000000000000000000000000000000000..825595390f4b32d71239cbf6439c8f01ea3f35ea
--- /dev/null
+++ b/Two-phase-Two-phase/one-patch/mesh_study/R-one-patch-mesh-study-alternative.py
@@ -0,0 +1,491 @@
+#!/usr/bin/python3
+import dolfin as df
+import mshr
+import numpy as np
+import sympy as sym
+import typing as tp
+import domainPatch as dp
+import LDDsimulation as ldd
+import functools as ft
+import helpers as hlp
+import datetime
+import os
+import pandas as pd
+
+date = datetime.datetime.now()
+datestr = date.strftime("%Y-%m-%d")
+#import ufl as ufl
+
+# init sympy session
+sym.init_printing()
+
+use_case = "R-one-patch-mesh-study"
+# solver_tol = 5E-9
+max_iter_num = 1000
+FEM_Lagrange_degree = 1
+mesh_study = True
+# resolutions = {128: 1e-7} #[1,2,3,4,5,10,20,40,75,100]
+resolutions = {
+                # 1: 1e-7,
+                # 2: 1e-7,
+                # 4: 1e-7,
+                # 8: 1e-7,
+                # 16: 1e-7,
+                32: 1e-7,
+                # 64: 1e-7,
+                # 128: 1e-7,
+                # 256: 1e-7,
+                # 512: 1e-7,
+                }
+
+############ GRID #######################
+# mesh_resolution = 20
+timestep_size = 0.001
+number_of_timesteps = 10
+plot_timestep_every = 1
+# decide how many timesteps you want analysed. Analysed means, that we write out
+# subsequent errors of the L-iteration within the timestep.
+number_of_timesteps_to_analyse = 5
+starttimes = [0.5]
+# starttimes = [0.0, 0.05]
+
+# starttimes = {
+#     1: 0.0
+#     2: 0.05
+#     4: 0.1
+#     8: 0.2
+#     16: 0.4
+#     32: 0.7
+#     64: 1.0
+#     128: 1.3
+# }
+
+Lw = 0.5 #/timestep_size
+Lnw=Lw
+
+lambda_w = 0
+lambda_nw = 0
+
+include_gravity = False
+debugflag = False
+analyse_condition = True
+
+if mesh_study:
+    output_string = "./output/{}-{}_timesteps{}_P{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree)
+else:
+    for tol in resolutions.values():
+        solver_tol = tol
+    output_string = "./output/{}-{}_timesteps{}_P{}_solver_tol{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree, solver_tol)
+
+# toggle what should be written to files
+if mesh_study:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': True,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+else:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': False,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+
+##### Domain and Interface ####
+# global simulation domain domain
+sub_domain0_vertices = [df.Point(-1.0, -1.0),  #
+                        df.Point(1.0, -1.0),  #
+                        df.Point(1.0, 1.0),  #
+                        df.Point(-1.0, 1.0)]
+
+subdomain0_outer_boundary_verts = {
+    0: [sub_domain0_vertices[0],
+        sub_domain0_vertices[1],
+        sub_domain0_vertices[2],
+        sub_domain0_vertices[3],
+        sub_domain0_vertices[0]]
+}
+
+# list of subdomains given by the boundary polygon vertices.
+# Subdomains are given as a list of dolfin points forming
+# a closed polygon, such that mshr.Polygon(subdomain_def_points[i]) can be used
+# to create the subdomain. subdomain_def_points[0] contains the
+# vertices of the global simulation domain and subdomain_def_points[i] contains the
+# vertices of the subdomain i.
+subdomain_def_points = [sub_domain0_vertices]
+# in the below list, index 0 corresponds to the 12 interface which has index 1
+interface_def_points = None
+
+# if a subdomain has no outer boundary write None instead, i.e.
+# i: None
+# if i is the index of the inner subdomain.
+outer_boundary_def_points = {
+    # subdomain number
+    0 : subdomain0_outer_boundary_verts
+}
+
+# adjacent_subdomains[i] contains the indices of the subdomains sharing the
+# interface i (i.e. given by interface_def_points[i]).
+adjacent_subdomains = None
+isRichards = {
+    0: True, #
+    }
+
+viscosity = {#
+# subdom_num : viscosity
+    0 : {'wetting' :1,
+         'nonwetting': 1}, #
+}
+
+porosity = {#
+# subdom_num : porosity
+    0: 1,#
+}
+
+# Dict of the form: { subdom_num : density }
+densities = {
+    0: {'wetting': 1,  #997,
+        'nonwetting': 1}, #1225}
+}
+
+gravity_acceleration = 9.81
+
+L = {#
+# subdom_num : subdomain L for L-scheme
+    0: {'wetting' :Lw,
+         'nonwetting': Lnw},#
+}
+
+lambda_param = {#
+# subdom_num : lambda parameter for the L-scheme
+    0: {'wetting' :lambda_w,
+         'nonwetting': lambda_nw},#
+}
+
+## relative permeabilty functions on subdomain 1
+def rel_perm1w(s):
+    # relative permeabilty wetting on subdomain1
+    return s**2
+
+def rel_perm1nw(s):
+    # relative permeabilty nonwetting on subdomain1
+    return (1-s)**2
+
+_rel_perm1w = ft.partial(rel_perm1w)
+_rel_perm1nw = ft.partial(rel_perm1nw)
+
+subdomain1_rel_perm = {
+    'wetting': _rel_perm1w,#
+    'nonwetting': _rel_perm1nw
+}
+
+## dictionary of relative permeabilties on all domains.
+relative_permeability = {#
+    0: subdomain1_rel_perm,
+}
+
+# definition of the derivatives of the relative permeabilities
+# relative permeabilty functions on subdomain 1
+def rel_perm1w_prime(s):
+    # relative permeabilty on subdomain1
+    return 2*s
+
+def rel_perm1nw_prime(s):
+    # relative permeabilty on subdomain1
+    return -2*(1-s)
+
+_rel_perm1w_prime = ft.partial(rel_perm1w_prime)
+_rel_perm1nw_prime = ft.partial(rel_perm1nw_prime)
+
+subdomain1_rel_perm_prime = {
+    'wetting': _rel_perm1w_prime,
+    'nonwetting': _rel_perm1nw_prime
+}
+
+# dictionary of relative permeabilties on all domains.
+ka_prime = {
+    0: subdomain1_rel_perm_prime,
+}
+
+
+
+def saturation(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return df.conditional(pc > 0, 1/((1 + pc)**(1/(index + 1))), 1)
+
+def saturation_sym(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return 1/((1 + pc)**(1/(index + 1)))
+
+
+# derivative of S-pc relationship with respect to pc. This is needed for the
+# construction of a analytic solution.
+def saturation_sym_prime(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return -1/((index+1)*(1 + pc)**((index+2)/(index+1)))
+
+
+# def saturation(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pc > 0, -index*pc, 1)
+#
+#
+# def saturation_sym(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index*pc
+#
+#
+# # derivative of S-pc relationship with respect to pc. This is needed for the
+# # construction of a analytic solution.
+# def saturation_sym_prime(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index
+
+
+# note that the conditional definition of S-pc in the nonsymbolic part will be
+# incorporated in the construction of the exact solution below.
+S_pc_sym = {
+    0: ft.partial(saturation_sym, index=1),
+}
+
+S_pc_sym_prime = {
+    0: ft.partial(saturation_sym_prime, index=1),
+}
+
+sat_pressure_relationship = {
+    0: ft.partial(saturation, index=1),
+}
+
+
+#############################################
+# Manufacture source expressions with sympy #
+#############################################
+x, y = sym.symbols('x[0], x[1]')  # needed by UFL
+t = sym.symbols('t', positive=True)
+
+epsilon_x_inner = 0.7
+epsilon_x_outer = 0.99
+epsilon_y_inner = epsilon_x_inner
+epsilon_y_outer = epsilon_x_outer
+
+def mollifier(x, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x/epsilon)**2) + 1)
+    return out_expr
+
+mollifier_handle = ft.partial(mollifier, epsilon=epsilon_x_inner)
+
+pw_sym_x = sym.Piecewise(
+    (mollifier_handle(x), x**2 < epsilon_x_outer**2),
+    (0, True)
+)
+pw_sym_y = sym.Piecewise(
+    (mollifier_handle(y), y**2 < epsilon_y_outer**2),
+    (0, True)
+)
+
+def mollifier2d(x, y, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x**2 + y**2)/epsilon**2) + 1)
+    return out_expr
+
+mollifier2d_handle = ft.partial(mollifier2d, epsilon=epsilon_x_outer)
+
+pw_sym2d_x = sym.Piecewise(
+    (mollifier2d_handle(x, y), x**2 + y**2 < epsilon_x_outer**2),
+    (0, True)
+)
+
+zero_on_epsilon_shrinking_of_subdomain = sym.Piecewise(
+    (mollifier_handle(sym.sqrt(x**2 + y**2)+2*epsilon_x_inner), ((-2*epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<=epsilon_x_inner))),
+    (mollifier_handle(sym.sqrt(x**2 + y**2)-2*epsilon_x_inner), ((epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_x = sym.Piecewise(
+    (mollifier_handle(x+2*epsilon_x_inner), ((-2*epsilon_x_inner<x) & (x<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=x) & (x<=epsilon_x_inner))),
+    (mollifier_handle(x-2*epsilon_x_inner), ((epsilon_x_inner<x) & (x<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_y = sym.Piecewise(
+    (1, y<=-2*epsilon_x_inner),
+    (mollifier_handle(y+2*epsilon_x_inner), ((-2*epsilon_x_inner<y) & (y<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=y) & (y<=epsilon_x_inner))),
+    (mollifier_handle(y-2*epsilon_x_inner), ((epsilon_x_inner<y) & (y<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_shrinking = zero_on_epsilon_shrinking_of_subdomain #zero_on_epsilon_shrinking_of_subdomain_x + zero_on_epsilon_shrinking_of_subdomain_y
+gaussian = pw_sym2d_x# pw_sym_y*pw_sym_x
+cutoff = gaussian/(gaussian + zero_on_shrinking)
+
+# # construction of differentiable characteristic function.
+# def smooth_characteristic_func_on_epsilon_shrinking_of_subdomain0(x, y, epsilon_x_inner, epsilon_y_inner, epsilon_x_outer, epsilon_y_outer):
+#     dist_to_complement_x = ft.partial(mollifier, epsilon=epsilon_x_inner)
+#     dist_to_complement_y = ft.partial(mollifier, epsilon=epsilon_y_inner)
+#     dist_to_complement = dist_to_complement_y(y)*dist_to_complement_x(x)
+#     dist_to_eps_shrinking_x = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_x_outer)
+#     dist_to_eps_shrinking_y = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_y_outer)
+#     dist_to_eps_shrinking = dist_to_eps_shrinking_y(y)*dist_to_eps_shrinking_x(x)
+#     return dist_to_complement/(dist_to_eps_shrinking + dist_to_complement)
+#
+
+# def dist_to_epsilon_thickening_of_subdomain0_complement(x, y, epsilon):
+#     """ calculates the (euklidian distance)^2 of a point x,y to the epsilon
+#         thickening of the complement of the domain.
+#     """
+#     is_inside = ((1-sym.Abs(x) > epsilon) & (1-sym.Abs(y) > epsilon))
+#     sym.Piecewise((0, is_inside))
+
+p_e_sym = {
+    0: {'wetting': (-7 -1*t*(1 + x + y)),  #*cutoff,
+        'nonwetting': (-1 -1*t*(1.1+y + x))},  #*cutoff},
+}
+
+pc_e_sym = dict()
+for subdomain, isR in isRichards.items():
+    if isR:
+        pc_e_sym.update({subdomain: -p_e_sym[subdomain]['wetting']})
+    else:
+        pc_e_sym.update({subdomain: p_e_sym[subdomain]['nonwetting']
+                                        - p_e_sym[subdomain]['wetting']})
+
+
+symbols = {"x": x,
+           "y": y,
+           "t": t}
+# turn above symbolic code into exact solution for dolphin and
+# construct the rhs that matches the above exact solution.
+exact_solution_example = hlp.generate_exact_solution_expressions(
+                        symbols=symbols,
+                        isRichards=isRichards,
+                        symbolic_pressure=p_e_sym,
+                        symbolic_capillary_pressure=pc_e_sym,
+                        saturation_pressure_relationship=S_pc_sym,
+                        saturation_pressure_relationship_prime=S_pc_sym_prime,
+                        viscosity=viscosity,
+                        porosity=porosity,
+                        relative_permeability=relative_permeability,
+                        relative_permeability_prime=ka_prime,
+                        densities=densities,
+                        gravity_acceleration=gravity_acceleration,
+                        include_gravity=include_gravity,
+                        )
+source_expression = exact_solution_example['source']
+exact_solution = exact_solution_example['exact_solution']
+initial_condition = exact_solution_example['initial_condition']
+
+# Dictionary of dirichlet boundary conditions.
+dirichletBC = dict()
+# similarly to the outer boundary dictionary, if a patch has no outer boundary
+# None should be written instead of an expression.
+# This is a bit of a brainfuck:
+# dirichletBC[ind] gives a dictionary of the outer boundaries of subdomain ind.
+# Since a domain patch can have several disjoint outer boundary parts, the
+# expressions need to get an enumaration index which starts at 0.
+# So dirichletBC[ind][j] is the dictionary of outer dirichlet conditions of
+# subdomain ind and boundary part j.
+# Finally, dirichletBC[ind][j]['wetting'] and dirichletBC[ind][j]['nonwetting']
+# return the actual expression needed for the dirichlet condition for both
+# phases if present.
+
+# subdomain index: {outer boudary part index: {phase: expression}}
+for subdomain in isRichards.keys():
+    # if subdomain has no outer boundary, outer_boundary_def_points[subdomain] is None
+    if outer_boundary_def_points[subdomain] is None:
+        dirichletBC.update({subdomain: None})
+    else:
+        dirichletBC.update({subdomain: dict()})
+        # set the dirichlet conditions to be the same code as exact solution on
+        # the subdomain.
+        for outer_boundary_ind in outer_boundary_def_points[subdomain].keys():
+            dirichletBC[subdomain].update(
+                {outer_boundary_ind: exact_solution[subdomain]}
+                )
+
+
+# def saturation(pressure, subdomain_index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pressure < 0, 1/((1 - pressure)**(1/(subdomain_index + 1))), 1)
+#
+# sa
+for starttime in starttimes:
+    for mesh_resolution, solver_tol in resolutions.items():
+        # initialise LDD simulation class
+        simulation = ldd.LDDsimulation(
+            tol=1E-14,
+            LDDsolver_tol=solver_tol,
+            debug=debugflag,
+            max_iter_num=max_iter_num,
+            FEM_Lagrange_degree=FEM_Lagrange_degree,
+            mesh_study=mesh_study
+            )
+
+        simulation.set_parameters(use_case=use_case,
+                                  output_dir=output_string,
+                                  subdomain_def_points=subdomain_def_points,
+                                  isRichards=isRichards,
+                                  interface_def_points=interface_def_points,
+                                  outer_boundary_def_points=outer_boundary_def_points,
+                                  adjacent_subdomains=adjacent_subdomains,
+                                  mesh_resolution=mesh_resolution,
+                                  viscosity=viscosity,
+                                  porosity=porosity,
+                                  L=L,
+                                  lambda_param=lambda_param,
+                                  relative_permeability=relative_permeability,
+                                  saturation=sat_pressure_relationship,
+                                  starttime=starttime,
+                                  number_of_timesteps=number_of_timesteps,
+                                  number_of_timesteps_to_analyse=number_of_timesteps_to_analyse,
+                                  plot_timestep_every=plot_timestep_every,
+                                  timestep_size=timestep_size,
+                                  sources=source_expression,
+                                  initial_conditions=initial_condition,
+                                  dirichletBC_expression_strings=dirichletBC,
+                                  exact_solution=exact_solution,
+                                  densities=densities,
+                                  include_gravity=include_gravity,
+                                  write2file=write_to_file,
+                                  )
+
+        simulation.initialise()
+        output_dir = simulation.output_dir
+        # simulation.write_exact_solution_to_xdmf()
+        output = simulation.run(analyse_condition=analyse_condition)
+        for subdomain_index, subdomain_output in output.items():
+            mesh_h = subdomain_output['mesh_size']
+            for phase, different_errornorms in subdomain_output['errornorm'].items():
+                filename = output_dir + "subdomain{}-space-time-errornorm-{}-phase.csv".format(subdomain_index, phase)
+                # for errortype, errornorm in different_errornorms.items():
+
+                    # eocfile = open("eoc_filename", "a")
+                    # eocfile.write( str(mesh_h) + " " + str(errornorm) + "\n" )
+                    # eocfile.close()
+                    # if subdomain.isRichards:mesh_h
+                data_dict = {
+                    'mesh_parameter': mesh_resolution,
+                    'mesh_h': mesh_h,
+                }
+                for error_type, errornorms in different_errornorms.items():
+                    data_dict.update(
+                        {error_type: errornorms}
+                    )
+                errors = pd.DataFrame(data_dict, index=[mesh_resolution])
+                # check if file exists
+                if os.path.isfile(filename) == True:
+                    with open(filename, 'a') as f:
+                        errors.to_csv(f, header=False, sep='\t', encoding='utf-8', index=False)
+                else:
+                    errors.to_csv(filename, sep='\t', encoding='utf-8', index=False)
diff --git a/Two-phase-Two-phase/one-patch/mesh_study/R-one-patch-mesh-study.py b/Two-phase-Two-phase/one-patch/mesh_study/R-one-patch-mesh-study.py
new file mode 100755
index 0000000000000000000000000000000000000000..ff81ca563e67101e3b0f2b6804c3e2717eaf2fda
--- /dev/null
+++ b/Two-phase-Two-phase/one-patch/mesh_study/R-one-patch-mesh-study.py
@@ -0,0 +1,491 @@
+#!/usr/bin/python3
+import dolfin as df
+import mshr
+import numpy as np
+import sympy as sym
+import typing as tp
+import domainPatch as dp
+import LDDsimulation as ldd
+import functools as ft
+import helpers as hlp
+import datetime
+import os
+import pandas as pd
+
+date = datetime.datetime.now()
+datestr = date.strftime("%Y-%m-%d")
+#import ufl as ufl
+
+# init sympy session
+sym.init_printing()
+
+use_case = "R-one-patch-mesh-study"
+# solver_tol = 5E-9
+max_iter_num = 1000
+FEM_Lagrange_degree = 1
+mesh_study = True
+# resolutions = {128: 1e-7} #[1,2,3,4,5,10,20,40,75,100]
+resolutions = {
+                # 1: 1e-7,
+                2: 1e-7,
+                4: 1e-7,
+                8: 1e-7,
+                16: 1e-7,
+                32: 1e-7,
+                64: 1e-7,
+                128: 1e-7,
+                256: 1e-7,
+                512: 1e-7,
+                }
+
+############ GRID #######################
+# mesh_resolution = 20
+timestep_size = 0.01
+number_of_timesteps = 70
+plot_timestep_every = 1
+# decide how many timesteps you want analysed. Analysed means, that we write out
+# subsequent errors of the L-iteration within the timestep.
+number_of_timesteps_to_analyse = 5
+starttimes = [0.0,0.25,0.5]
+# starttimes = [0.0, 0.05]
+
+# starttimes = {
+#     1: 0.0
+#     2: 0.05
+#     4: 0.1
+#     8: 0.2
+#     16: 0.4
+#     32: 0.7
+#     64: 1.0
+#     128: 1.3
+# }
+
+Lw = 0.025 #/timestep_size
+Lnw=Lw
+
+lambda_w = 0
+lambda_nw = 0
+
+include_gravity = True
+debugflag = False
+analyse_condition = False
+
+if mesh_study:
+    output_string = "./output/{}-{}_timesteps{}_P{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree)
+else:
+    for tol in resolutions.values():
+        solver_tol = tol
+    output_string = "./output/{}-{}_timesteps{}_P{}_solver_tol{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree, solver_tol)
+
+# toggle what should be written to files
+if mesh_study:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': True,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+else:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': False,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+
+##### Domain and Interface ####
+# global simulation domain domain
+sub_domain0_vertices = [df.Point(-1.0, -1.0),  #
+                        df.Point(1.0, -1.0),  #
+                        df.Point(1.0, 1.0),  #
+                        df.Point(-1.0, 1.0)]
+
+subdomain0_outer_boundary_verts = {
+    0: [sub_domain0_vertices[0],
+        sub_domain0_vertices[1],
+        sub_domain0_vertices[2],
+        sub_domain0_vertices[3],
+        sub_domain0_vertices[0]]
+}
+
+# list of subdomains given by the boundary polygon vertices.
+# Subdomains are given as a list of dolfin points forming
+# a closed polygon, such that mshr.Polygon(subdomain_def_points[i]) can be used
+# to create the subdomain. subdomain_def_points[0] contains the
+# vertices of the global simulation domain and subdomain_def_points[i] contains the
+# vertices of the subdomain i.
+subdomain_def_points = [sub_domain0_vertices]
+# in the below list, index 0 corresponds to the 12 interface which has index 1
+interface_def_points = None
+
+# if a subdomain has no outer boundary write None instead, i.e.
+# i: None
+# if i is the index of the inner subdomain.
+outer_boundary_def_points = {
+    # subdomain number
+    0 : subdomain0_outer_boundary_verts
+}
+
+# adjacent_subdomains[i] contains the indices of the subdomains sharing the
+# interface i (i.e. given by interface_def_points[i]).
+adjacent_subdomains = None
+isRichards = {
+    0: True, #
+    }
+
+viscosity = {#
+# subdom_num : viscosity
+    0 : {'wetting' :1,
+         'nonwetting': 1}, #
+}
+
+porosity = {#
+# subdom_num : porosity
+    0: 1,#
+}
+
+# Dict of the form: { subdom_num : density }
+densities = {
+    0: {'wetting': 1,  #997,
+        'nonwetting': 1}, #1225}
+}
+
+gravity_acceleration = 9.81
+
+L = {#
+# subdom_num : subdomain L for L-scheme
+    0: {'wetting' :Lw,
+         'nonwetting': Lnw},#
+}
+
+lambda_param = {#
+# subdom_num : lambda parameter for the L-scheme
+    0: {'wetting' :lambda_w,
+         'nonwetting': lambda_nw},#
+}
+
+## relative permeabilty functions on subdomain 1
+def rel_perm1w(s):
+    # relative permeabilty wetting on subdomain1
+    return s**2
+
+def rel_perm1nw(s):
+    # relative permeabilty nonwetting on subdomain1
+    return (1-s)**2
+
+_rel_perm1w = ft.partial(rel_perm1w)
+_rel_perm1nw = ft.partial(rel_perm1nw)
+
+subdomain1_rel_perm = {
+    'wetting': _rel_perm1w,#
+    'nonwetting': _rel_perm1nw
+}
+
+## dictionary of relative permeabilties on all domains.
+relative_permeability = {#
+    0: subdomain1_rel_perm,
+}
+
+# definition of the derivatives of the relative permeabilities
+# relative permeabilty functions on subdomain 1
+def rel_perm1w_prime(s):
+    # relative permeabilty on subdomain1
+    return 2*s
+
+def rel_perm1nw_prime(s):
+    # relative permeabilty on subdomain1
+    return -2*(1-s)
+
+_rel_perm1w_prime = ft.partial(rel_perm1w_prime)
+_rel_perm1nw_prime = ft.partial(rel_perm1nw_prime)
+
+subdomain1_rel_perm_prime = {
+    'wetting': _rel_perm1w_prime,
+    'nonwetting': _rel_perm1nw_prime
+}
+
+# dictionary of relative permeabilties on all domains.
+ka_prime = {
+    0: subdomain1_rel_perm_prime,
+}
+
+
+
+def saturation(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return df.conditional(pc > 0, 1/((1 + pc)**(1/(index + 1))), 1)
+
+def saturation_sym(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return 1/((1 + pc)**(1/(index + 1)))
+
+
+# derivative of S-pc relationship with respect to pc. This is needed for the
+# construction of a analytic solution.
+def saturation_sym_prime(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return -1/((index+1)*(1 + pc)**((index+2)/(index+1)))
+
+
+# def saturation(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pc > 0, -index*pc, 1)
+#
+#
+# def saturation_sym(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index*pc
+#
+#
+# # derivative of S-pc relationship with respect to pc. This is needed for the
+# # construction of a analytic solution.
+# def saturation_sym_prime(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index
+
+
+# note that the conditional definition of S-pc in the nonsymbolic part will be
+# incorporated in the construction of the exact solution below.
+S_pc_sym = {
+    0: ft.partial(saturation_sym, index=1),
+}
+
+S_pc_sym_prime = {
+    0: ft.partial(saturation_sym_prime, index=1),
+}
+
+sat_pressure_relationship = {
+    0: ft.partial(saturation, index=1),
+}
+
+
+#############################################
+# Manufacture source expressions with sympy #
+#############################################
+x, y = sym.symbols('x[0], x[1]')  # needed by UFL
+t = sym.symbols('t', positive=True)
+
+epsilon_x_inner = 0.7
+epsilon_x_outer = 0.99
+epsilon_y_inner = epsilon_x_inner
+epsilon_y_outer = epsilon_x_outer
+
+def mollifier(x, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x/epsilon)**2) + 1)
+    return out_expr
+
+mollifier_handle = ft.partial(mollifier, epsilon=epsilon_x_inner)
+
+pw_sym_x = sym.Piecewise(
+    (mollifier_handle(x), x**2 < epsilon_x_outer**2),
+    (0, True)
+)
+pw_sym_y = sym.Piecewise(
+    (mollifier_handle(y), y**2 < epsilon_y_outer**2),
+    (0, True)
+)
+
+def mollifier2d(x, y, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x**2 + y**2)/epsilon**2) + 1)
+    return out_expr
+
+mollifier2d_handle = ft.partial(mollifier2d, epsilon=epsilon_x_outer)
+
+pw_sym2d_x = sym.Piecewise(
+    (mollifier2d_handle(x, y), x**2 + y**2 < epsilon_x_outer**2),
+    (0, True)
+)
+
+zero_on_epsilon_shrinking_of_subdomain = sym.Piecewise(
+    (mollifier_handle(sym.sqrt(x**2 + y**2)+2*epsilon_x_inner), ((-2*epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<=epsilon_x_inner))),
+    (mollifier_handle(sym.sqrt(x**2 + y**2)-2*epsilon_x_inner), ((epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_x = sym.Piecewise(
+    (mollifier_handle(x+2*epsilon_x_inner), ((-2*epsilon_x_inner<x) & (x<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=x) & (x<=epsilon_x_inner))),
+    (mollifier_handle(x-2*epsilon_x_inner), ((epsilon_x_inner<x) & (x<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_y = sym.Piecewise(
+    (1, y<=-2*epsilon_x_inner),
+    (mollifier_handle(y+2*epsilon_x_inner), ((-2*epsilon_x_inner<y) & (y<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=y) & (y<=epsilon_x_inner))),
+    (mollifier_handle(y-2*epsilon_x_inner), ((epsilon_x_inner<y) & (y<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_shrinking = zero_on_epsilon_shrinking_of_subdomain #zero_on_epsilon_shrinking_of_subdomain_x + zero_on_epsilon_shrinking_of_subdomain_y
+gaussian = pw_sym2d_x# pw_sym_y*pw_sym_x
+cutoff = gaussian/(gaussian + zero_on_shrinking)
+
+# # construction of differentiable characteristic function.
+# def smooth_characteristic_func_on_epsilon_shrinking_of_subdomain0(x, y, epsilon_x_inner, epsilon_y_inner, epsilon_x_outer, epsilon_y_outer):
+#     dist_to_complement_x = ft.partial(mollifier, epsilon=epsilon_x_inner)
+#     dist_to_complement_y = ft.partial(mollifier, epsilon=epsilon_y_inner)
+#     dist_to_complement = dist_to_complement_y(y)*dist_to_complement_x(x)
+#     dist_to_eps_shrinking_x = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_x_outer)
+#     dist_to_eps_shrinking_y = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_y_outer)
+#     dist_to_eps_shrinking = dist_to_eps_shrinking_y(y)*dist_to_eps_shrinking_x(x)
+#     return dist_to_complement/(dist_to_eps_shrinking + dist_to_complement)
+#
+
+# def dist_to_epsilon_thickening_of_subdomain0_complement(x, y, epsilon):
+#     """ calculates the (euklidian distance)^2 of a point x,y to the epsilon
+#         thickening of the complement of the domain.
+#     """
+#     is_inside = ((1-sym.Abs(x) > epsilon) & (1-sym.Abs(y) > epsilon))
+#     sym.Piecewise((0, is_inside))
+
+p_e_sym = {
+    0: {'wetting': (-7 - (1+t*t)*(1 + x*x + y*y)),  #*cutoff,
+        'nonwetting': (-1 -t*(1.1+y + x**2))},  #*cutoff},
+}
+
+pc_e_sym = dict()
+for subdomain, isR in isRichards.items():
+    if isR:
+        pc_e_sym.update({subdomain: -p_e_sym[subdomain]['wetting']})
+    else:
+        pc_e_sym.update({subdomain: p_e_sym[subdomain]['nonwetting']
+                                        - p_e_sym[subdomain]['wetting']})
+
+
+symbols = {"x": x,
+           "y": y,
+           "t": t}
+# turn above symbolic code into exact solution for dolphin and
+# construct the rhs that matches the above exact solution.
+exact_solution_example = hlp.generate_exact_solution_expressions(
+                        symbols=symbols,
+                        isRichards=isRichards,
+                        symbolic_pressure=p_e_sym,
+                        symbolic_capillary_pressure=pc_e_sym,
+                        saturation_pressure_relationship=S_pc_sym,
+                        saturation_pressure_relationship_prime=S_pc_sym_prime,
+                        viscosity=viscosity,
+                        porosity=porosity,
+                        relative_permeability=relative_permeability,
+                        relative_permeability_prime=ka_prime,
+                        densities=densities,
+                        gravity_acceleration=gravity_acceleration,
+                        include_gravity=include_gravity,
+                        )
+source_expression = exact_solution_example['source']
+exact_solution = exact_solution_example['exact_solution']
+initial_condition = exact_solution_example['initial_condition']
+
+# Dictionary of dirichlet boundary conditions.
+dirichletBC = dict()
+# similarly to the outer boundary dictionary, if a patch has no outer boundary
+# None should be written instead of an expression.
+# This is a bit of a brainfuck:
+# dirichletBC[ind] gives a dictionary of the outer boundaries of subdomain ind.
+# Since a domain patch can have several disjoint outer boundary parts, the
+# expressions need to get an enumaration index which starts at 0.
+# So dirichletBC[ind][j] is the dictionary of outer dirichlet conditions of
+# subdomain ind and boundary part j.
+# Finally, dirichletBC[ind][j]['wetting'] and dirichletBC[ind][j]['nonwetting']
+# return the actual expression needed for the dirichlet condition for both
+# phases if present.
+
+# subdomain index: {outer boudary part index: {phase: expression}}
+for subdomain in isRichards.keys():
+    # if subdomain has no outer boundary, outer_boundary_def_points[subdomain] is None
+    if outer_boundary_def_points[subdomain] is None:
+        dirichletBC.update({subdomain: None})
+    else:
+        dirichletBC.update({subdomain: dict()})
+        # set the dirichlet conditions to be the same code as exact solution on
+        # the subdomain.
+        for outer_boundary_ind in outer_boundary_def_points[subdomain].keys():
+            dirichletBC[subdomain].update(
+                {outer_boundary_ind: exact_solution[subdomain]}
+                )
+
+
+# def saturation(pressure, subdomain_index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pressure < 0, 1/((1 - pressure)**(1/(subdomain_index + 1))), 1)
+#
+# sa
+for starttime in starttimes:
+    for mesh_resolution, solver_tol in resolutions.items():
+        # initialise LDD simulation class
+        simulation = ldd.LDDsimulation(
+            tol=1E-14,
+            LDDsolver_tol=solver_tol,
+            debug=debugflag,
+            max_iter_num=max_iter_num,
+            FEM_Lagrange_degree=FEM_Lagrange_degree,
+            mesh_study=mesh_study
+            )
+
+        simulation.set_parameters(use_case=use_case,
+                                  output_dir=output_string,
+                                  subdomain_def_points=subdomain_def_points,
+                                  isRichards=isRichards,
+                                  interface_def_points=interface_def_points,
+                                  outer_boundary_def_points=outer_boundary_def_points,
+                                  adjacent_subdomains=adjacent_subdomains,
+                                  mesh_resolution=mesh_resolution,
+                                  viscosity=viscosity,
+                                  porosity=porosity,
+                                  L=L,
+                                  lambda_param=lambda_param,
+                                  relative_permeability=relative_permeability,
+                                  saturation=sat_pressure_relationship,
+                                  starttime=starttime,
+                                  number_of_timesteps=number_of_timesteps,
+                                  number_of_timesteps_to_analyse=number_of_timesteps_to_analyse,
+                                  plot_timestep_every=plot_timestep_every,
+                                  timestep_size=timestep_size,
+                                  sources=source_expression,
+                                  initial_conditions=initial_condition,
+                                  dirichletBC_expression_strings=dirichletBC,
+                                  exact_solution=exact_solution,
+                                  densities=densities,
+                                  include_gravity=include_gravity,
+                                  write2file=write_to_file,
+                                  )
+
+        simulation.initialise()
+        output_dir = simulation.output_dir
+        # simulation.write_exact_solution_to_xdmf()
+        output = simulation.run(analyse_condition=analyse_condition)
+        for subdomain_index, subdomain_output in output.items():
+            mesh_h = subdomain_output['mesh_size']
+            for phase, different_errornorms in subdomain_output['errornorm'].items():
+                filename = output_dir + "subdomain{}-space-time-errornorm-{}-phase.csv".format(subdomain_index, phase)
+                # for errortype, errornorm in different_errornorms.items():
+
+                    # eocfile = open("eoc_filename", "a")
+                    # eocfile.write( str(mesh_h) + " " + str(errornorm) + "\n" )
+                    # eocfile.close()
+                    # if subdomain.isRichards:mesh_h
+                data_dict = {
+                    'mesh_parameter': mesh_resolution,
+                    'mesh_h': mesh_h,
+                }
+                for error_type, errornorms in different_errornorms.items():
+                    data_dict.update(
+                        {error_type: errornorms}
+                    )
+                errors = pd.DataFrame(data_dict, index=[mesh_resolution])
+                # check if file exists
+                if os.path.isfile(filename) == True:
+                    with open(filename, 'a') as f:
+                        errors.to_csv(f, header=False, sep='\t', encoding='utf-8', index=False)
+                else:
+                    errors.to_csv(filename, sep='\t', encoding='utf-8', index=False)
diff --git a/Two-phase-Two-phase/one-patch/mesh_study/TP-one-patch-mesh-study.py b/Two-phase-Two-phase/one-patch/mesh_study/TP-one-patch-mesh-study.py
new file mode 100755
index 0000000000000000000000000000000000000000..bed62b609b08a817ee764588d230195c31e6a9d2
--- /dev/null
+++ b/Two-phase-Two-phase/one-patch/mesh_study/TP-one-patch-mesh-study.py
@@ -0,0 +1,471 @@
+#!/usr/bin/python3
+import dolfin as df
+import mshr
+import numpy as np
+import sympy as sym
+import typing as tp
+import domainPatch as dp
+import LDDsimulation as ldd
+import functools as ft
+import helpers as hlp
+import datetime
+import os
+import pandas as pd
+
+date = datetime.datetime.now()
+datestr = date.strftime("%Y-%m-%d")
+#import ufl as ufl
+
+# init sympy session
+sym.init_printing()
+
+use_case = "TP-one-patch"
+# solver_tol = 5E-9
+max_iter_num = 500
+FEM_Lagrange_degree = 1
+mesh_study = True
+# resolutions = {128: 1e-7} #[1,2,3,4,5,10,20,40,75,100]
+resolutions = { 1: 1e-7,
+                2: 1e-7,
+                4: 1e-7,
+                8: 1e-7,
+                16: 1e-7,
+                32: 1e-7,
+                64: 1e-7,
+                128: 1e-7,
+                256: 1e-7}
+
+############ GRID #######################
+# mesh_resolution = 20
+timestep_size = 0.01
+number_of_timesteps = 80
+plot_timestep_every = 1
+# decide how many timesteps you want analysed. Analysed means, that we write out
+# subsequent errors of the L-iteration within the timestep.
+number_of_timesteps_to_analyse = 4
+starttime = 0.0
+
+Lw = 0.025 #/timestep_size
+Lnw=Lw
+
+lambda_w = 40
+lambda_nw = 40
+
+include_gravity = False
+debugflag = False
+analyse_condition = False
+
+output_string = "./output/{}-{}_timesteps{}_P{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree)
+
+# toggle what should be written to files
+if mesh_study:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': False,
+        'solutions': True,
+        'absolute_differences': False,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+else:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': False,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+
+##### Domain and Interface ####
+# global simulation domain domain
+sub_domain0_vertices = [df.Point(-1.0, -1.0),  #
+                        df.Point(1.0, -1.0),  #
+                        df.Point(1.0, 1.0),  #
+                        df.Point(-1.0, 1.0)]
+
+subdomain0_outer_boundary_verts = {
+    0: [sub_domain0_vertices[0],
+        sub_domain0_vertices[1],
+        sub_domain0_vertices[2],
+        sub_domain0_vertices[3],
+        sub_domain0_vertices[0]]
+}
+
+# list of subdomains given by the boundary polygon vertices.
+# Subdomains are given as a list of dolfin points forming
+# a closed polygon, such that mshr.Polygon(subdomain_def_points[i]) can be used
+# to create the subdomain. subdomain_def_points[0] contains the
+# vertices of the global simulation domain and subdomain_def_points[i] contains the
+# vertices of the subdomain i.
+subdomain_def_points = [sub_domain0_vertices]
+# in the below list, index 0 corresponds to the 12 interface which has index 1
+interface_def_points = None
+
+# if a subdomain has no outer boundary write None instead, i.e.
+# i: None
+# if i is the index of the inner subdomain.
+outer_boundary_def_points = {
+    # subdomain number
+    0 : subdomain0_outer_boundary_verts
+}
+
+# adjacent_subdomains[i] contains the indices of the subdomains sharing the
+# interface i (i.e. given by interface_def_points[i]).
+adjacent_subdomains = None
+isRichards = {
+    0: False, #
+    }
+
+viscosity = {#
+# subdom_num : viscosity
+    0 : {'wetting' :1,
+         'nonwetting': 1}, #
+}
+
+porosity = {#
+# subdom_num : porosity
+    0: 1,#
+}
+
+# Dict of the form: { subdom_num : density }
+densities = {
+    0: {'wetting': 1,  #997,
+        'nonwetting': 1}, #1225}
+}
+
+gravity_acceleration = 9.81
+
+L = {#
+# subdom_num : subdomain L for L-scheme
+    0: {'wetting' :Lw,
+         'nonwetting': Lnw},#
+}
+
+lambda_param = {#
+# subdom_num : lambda parameter for the L-scheme
+    0: {'wetting' :lambda_w,
+         'nonwetting': lambda_nw},#
+}
+
+## relative permeabilty functions on subdomain 1
+def rel_perm1w(s):
+    # relative permeabilty wetting on subdomain1
+    return s**2
+
+def rel_perm1nw(s):
+    # relative permeabilty nonwetting on subdomain1
+    return (1-s)**2
+
+_rel_perm1w = ft.partial(rel_perm1w)
+_rel_perm1nw = ft.partial(rel_perm1nw)
+
+subdomain1_rel_perm = {
+    'wetting': _rel_perm1w,#
+    'nonwetting': _rel_perm1nw
+}
+
+## dictionary of relative permeabilties on all domains.
+relative_permeability = {#
+    0: subdomain1_rel_perm,
+}
+
+# definition of the derivatives of the relative permeabilities
+# relative permeabilty functions on subdomain 1
+def rel_perm1w_prime(s):
+    # relative permeabilty on subdomain1
+    return 2*s
+
+def rel_perm1nw_prime(s):
+    # relative permeabilty on subdomain1
+    return -2*(1-s)
+
+_rel_perm1w_prime = ft.partial(rel_perm1w_prime)
+_rel_perm1nw_prime = ft.partial(rel_perm1nw_prime)
+
+subdomain1_rel_perm_prime = {
+    'wetting': _rel_perm1w_prime,
+    'nonwetting': _rel_perm1nw_prime
+}
+
+# dictionary of relative permeabilties on all domains.
+ka_prime = {
+    0: subdomain1_rel_perm_prime,
+}
+
+
+
+def saturation(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return df.conditional(pc > 0, 1/((1 + pc)**(1/(index + 1))), 1)
+
+def saturation_sym(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return 1/((1 + pc)**(1/(index + 1)))
+
+
+# derivative of S-pc relationship with respect to pc. This is needed for the
+# construction of a analytic solution.
+def saturation_sym_prime(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return -1/((index+1)*(1 + pc)**((index+2)/(index+1)))
+
+
+# def saturation(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pc > 0, -index*pc, 1)
+#
+#
+# def saturation_sym(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index*pc
+#
+#
+# # derivative of S-pc relationship with respect to pc. This is needed for the
+# # construction of a analytic solution.
+# def saturation_sym_prime(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index
+
+
+# note that the conditional definition of S-pc in the nonsymbolic part will be
+# incorporated in the construction of the exact solution below.
+S_pc_sym = {
+    0: ft.partial(saturation_sym, index=1),
+}
+
+S_pc_sym_prime = {
+    0: ft.partial(saturation_sym_prime, index=1),
+}
+
+sat_pressure_relationship = {
+    0: ft.partial(saturation, index=1),
+}
+
+
+#############################################
+# Manufacture source expressions with sympy #
+#############################################
+x, y = sym.symbols('x[0], x[1]')  # needed by UFL
+t = sym.symbols('t', positive=True)
+
+epsilon_x_inner = 0.7
+epsilon_x_outer = 0.99
+epsilon_y_inner = epsilon_x_inner
+epsilon_y_outer = epsilon_x_outer
+
+def mollifier(x, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x/epsilon)**2) + 1)
+    return out_expr
+
+mollifier_handle = ft.partial(mollifier, epsilon=epsilon_x_inner)
+
+pw_sym_x = sym.Piecewise(
+    (mollifier_handle(x), x**2 < epsilon_x_outer**2),
+    (0, True)
+)
+pw_sym_y = sym.Piecewise(
+    (mollifier_handle(y), y**2 < epsilon_y_outer**2),
+    (0, True)
+)
+
+def mollifier2d(x, y, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x**2 + y**2)/epsilon**2) + 1)
+    return out_expr
+
+mollifier2d_handle = ft.partial(mollifier2d, epsilon=epsilon_x_outer)
+
+pw_sym2d_x = sym.Piecewise(
+    (mollifier2d_handle(x, y), x**2 + y**2 < epsilon_x_outer**2),
+    (0, True)
+)
+
+zero_on_epsilon_shrinking_of_subdomain = sym.Piecewise(
+    (mollifier_handle(sym.sqrt(x**2 + y**2)+2*epsilon_x_inner), ((-2*epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<=epsilon_x_inner))),
+    (mollifier_handle(sym.sqrt(x**2 + y**2)-2*epsilon_x_inner), ((epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_x = sym.Piecewise(
+    (mollifier_handle(x+2*epsilon_x_inner), ((-2*epsilon_x_inner<x) & (x<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=x) & (x<=epsilon_x_inner))),
+    (mollifier_handle(x-2*epsilon_x_inner), ((epsilon_x_inner<x) & (x<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_y = sym.Piecewise(
+    (1, y<=-2*epsilon_x_inner),
+    (mollifier_handle(y+2*epsilon_x_inner), ((-2*epsilon_x_inner<y) & (y<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=y) & (y<=epsilon_x_inner))),
+    (mollifier_handle(y-2*epsilon_x_inner), ((epsilon_x_inner<y) & (y<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_shrinking = zero_on_epsilon_shrinking_of_subdomain #zero_on_epsilon_shrinking_of_subdomain_x + zero_on_epsilon_shrinking_of_subdomain_y
+gaussian = pw_sym2d_x# pw_sym_y*pw_sym_x
+cutoff = gaussian/(gaussian + zero_on_shrinking)
+
+# # construction of differentiable characteristic function.
+# def smooth_characteristic_func_on_epsilon_shrinking_of_subdomain0(x, y, epsilon_x_inner, epsilon_y_inner, epsilon_x_outer, epsilon_y_outer):
+#     dist_to_complement_x = ft.partial(mollifier, epsilon=epsilon_x_inner)
+#     dist_to_complement_y = ft.partial(mollifier, epsilon=epsilon_y_inner)
+#     dist_to_complement = dist_to_complement_y(y)*dist_to_complement_x(x)
+#     dist_to_eps_shrinking_x = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_x_outer)
+#     dist_to_eps_shrinking_y = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_y_outer)
+#     dist_to_eps_shrinking = dist_to_eps_shrinking_y(y)*dist_to_eps_shrinking_x(x)
+#     return dist_to_complement/(dist_to_eps_shrinking + dist_to_complement)
+#
+
+# def dist_to_epsilon_thickening_of_subdomain0_complement(x, y, epsilon):
+#     """ calculates the (euklidian distance)^2 of a point x,y to the epsilon
+#         thickening of the complement of the domain.
+#     """
+#     is_inside = ((1-sym.Abs(x) > epsilon) & (1-sym.Abs(y) > epsilon))
+#     sym.Piecewise((0, is_inside))
+
+p_e_sym = {
+    0: {'wetting': (-7 - (1+t*t)*(1 + x*x + y*y)),  #*cutoff,
+        'nonwetting': (-1 -t*(1.1+y + x**2))},  #*cutoff},
+}
+
+pc_e_sym = dict()
+for subdomain, isR in isRichards.items():
+    if isR:
+        pc_e_sym.update({subdomain: -p_e_sym[subdomain]['wetting']})
+    else:
+        pc_e_sym.update({subdomain: p_e_sym[subdomain]['nonwetting']
+                                        - p_e_sym[subdomain]['wetting']})
+
+
+symbols = {"x": x,
+           "y": y,
+           "t": t}
+# turn above symbolic code into exact solution for dolphin and
+# construct the rhs that matches the above exact solution.
+exact_solution_example = hlp.generate_exact_solution_expressions(
+                        symbols=symbols,
+                        isRichards=isRichards,
+                        symbolic_pressure=p_e_sym,
+                        symbolic_capillary_pressure=pc_e_sym,
+                        saturation_pressure_relationship=S_pc_sym,
+                        saturation_pressure_relationship_prime=S_pc_sym_prime,
+                        viscosity=viscosity,
+                        porosity=porosity,
+                        relative_permeability=relative_permeability,
+                        relative_permeability_prime=ka_prime,
+                        densities=densities,
+                        gravity_acceleration=gravity_acceleration,
+                        include_gravity=include_gravity,
+                        )
+source_expression = exact_solution_example['source']
+exact_solution = exact_solution_example['exact_solution']
+initial_condition = exact_solution_example['initial_condition']
+
+# Dictionary of dirichlet boundary conditions.
+dirichletBC = dict()
+# similarly to the outer boundary dictionary, if a patch has no outer boundary
+# None should be written instead of an expression.
+# This is a bit of a brainfuck:
+# dirichletBC[ind] gives a dictionary of the outer boundaries of subdomain ind.
+# Since a domain patch can have several disjoint outer boundary parts, the
+# expressions need to get an enumaration index which starts at 0.
+# So dirichletBC[ind][j] is the dictionary of outer dirichlet conditions of
+# subdomain ind and boundary part j.
+# Finally, dirichletBC[ind][j]['wetting'] and dirichletBC[ind][j]['nonwetting']
+# return the actual expression needed for the dirichlet condition for both
+# phases if present.
+
+# subdomain index: {outer boudary part index: {phase: expression}}
+for subdomain in isRichards.keys():
+    # if subdomain has no outer boundary, outer_boundary_def_points[subdomain] is None
+    if outer_boundary_def_points[subdomain] is None:
+        dirichletBC.update({subdomain: None})
+    else:
+        dirichletBC.update({subdomain: dict()})
+        # set the dirichlet conditions to be the same code as exact solution on
+        # the subdomain.
+        for outer_boundary_ind in outer_boundary_def_points[subdomain].keys():
+            dirichletBC[subdomain].update(
+                {outer_boundary_ind: exact_solution[subdomain]}
+                )
+
+
+# def saturation(pressure, subdomain_index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pressure < 0, 1/((1 - pressure)**(1/(subdomain_index + 1))), 1)
+#
+# sa
+
+for mesh_resolution, solver_tol in resolutions.items():
+    # initialise LDD simulation class
+    simulation = ldd.LDDsimulation(
+        tol=1E-14,
+        LDDsolver_tol=solver_tol,
+        debug=debugflag,
+        max_iter_num=max_iter_num,
+        FEM_Lagrange_degree=FEM_Lagrange_degree,
+        mesh_study=mesh_study
+        )
+
+    simulation.set_parameters(use_case=use_case,
+                              output_dir=output_string,
+                              subdomain_def_points=subdomain_def_points,
+                              isRichards=isRichards,
+                              interface_def_points=interface_def_points,
+                              outer_boundary_def_points=outer_boundary_def_points,
+                              adjacent_subdomains=adjacent_subdomains,
+                              mesh_resolution=mesh_resolution,
+                              viscosity=viscosity,
+                              porosity=porosity,
+                              L=L,
+                              lambda_param=lambda_param,
+                              relative_permeability=relative_permeability,
+                              saturation=sat_pressure_relationship,
+                              starttime=starttime,
+                              number_of_timesteps=number_of_timesteps,
+                              number_of_timesteps_to_analyse=number_of_timesteps_to_analyse,
+                              plot_timestep_every=plot_timestep_every,
+                              timestep_size=timestep_size,
+                              sources=source_expression,
+                              initial_conditions=initial_condition,
+                              dirichletBC_expression_strings=dirichletBC,
+                              exact_solution=exact_solution,
+                              densities=densities,
+                              include_gravity=include_gravity,
+                              write2file=write_to_file,
+                              )
+
+    simulation.initialise()
+    output_dir = simulation.output_dir
+    # simulation.write_exact_solution_to_xdmf()
+    output = simulation.run(analyse_condition=analyse_condition)
+    for subdomain_index, subdomain_output in output.items():
+        mesh_h = subdomain_output['mesh_size']
+        for phase, different_errornorms in subdomain_output['errornorm'].items():
+            filename = output_dir + "subdomain{}-space-time-errornorm-{}-phase.csv".format(subdomain_index, phase)
+            # for errortype, errornorm in different_errornorms.items():
+
+                # eocfile = open("eoc_filename", "a")
+                # eocfile.write( str(mesh_h) + " " + str(errornorm) + "\n" )
+                # eocfile.close()
+                # if subdomain.isRichards:mesh_h
+            data_dict = {
+                'mesh_parameter': mesh_resolution,
+                'mesh_h': mesh_h,
+            }
+            for error_type, errornorms in different_errornorms.items():
+                data_dict.update(
+                    {error_type: errornorms}
+                )
+            errors = pd.DataFrame(data_dict, index=[mesh_resolution])
+            # check if file exists
+            if os.path.isfile(filename) == True:
+                with open(filename, 'a') as f:
+                    errors.to_csv(f, header=False, sep='\t', encoding='utf-8', index=False)
+            else:
+                errors.to_csv(filename, sep='\t', encoding='utf-8', index=False)
diff --git a/Two-phase-Two-phase/one-patch/mesh_study/run-simulation b/Two-phase-Two-phase/one-patch/mesh_study/run-simulation
new file mode 100755
index 0000000000000000000000000000000000000000..0eb497502a082a0fec07a5449b1fe946d59c8cc7
--- /dev/null
+++ b/Two-phase-Two-phase/one-patch/mesh_study/run-simulation
@@ -0,0 +1,16 @@
+#!/bin/bash
+
+[ $# -eq 0 ] && { echo "Usage: $0 simulation_file [logfile_name]"; exit 1; }
+
+SIMULATION_FILE=$1
+SIMULATION=${SIMULATION_FILE%.py}
+LOGFILE_DEFAULT="$SIMULATION.log"
+
+DATE=$(date -I)
+LOGFILE=${2:-$DATE-$LOGFILE_DEFAULT}
+
+GREETING="Simulation $SIMULATION is run on $DATE by $USER"
+
+echo $GREETING
+echo "running $SIMULATION_FILE | tee $LOGFILE"
+./$SIMULATION_FILE | tee $LOGFILE
diff --git a/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/R-one-patch-mesh-study-fixed-timestep.py b/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/R-one-patch-mesh-study-fixed-timestep.py
new file mode 100755
index 0000000000000000000000000000000000000000..14677c93cdbe98edb0217fbb0021084a48e7e232
--- /dev/null
+++ b/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/R-one-patch-mesh-study-fixed-timestep.py
@@ -0,0 +1,491 @@
+#!/usr/bin/python3
+import dolfin as df
+import mshr
+import numpy as np
+import sympy as sym
+import typing as tp
+import domainPatch as dp
+import LDDsimulation as ldd
+import functools as ft
+import helpers as hlp
+import datetime
+import os
+import pandas as pd
+
+date = datetime.datetime.now()
+datestr = date.strftime("%Y-%m-%d")
+#import ufl as ufl
+
+# init sympy session
+sym.init_printing()
+
+use_case = "R-one-patch-mesh-study-fixed-timestep-new-errornorm"
+# solver_tol = 5E-9
+max_iter_num = 1000
+FEM_Lagrange_degree = 1
+mesh_study = True
+# resolutions = {128: 1e-8} #[1,2,3,4,5,10,20,40,75,100]
+resolutions = {
+                1: 1e-8,
+                2: 1e-8,
+                4: 1e-8,
+                8: 1e-8,
+                16: 1e-8,
+                32: 1e-8,
+                64: 1e-8,
+                # 128: 1e-8,
+                # 256: 1e-8,
+                # 512: 1e-8,
+                }
+
+############ GRID #######################
+# mesh_resolution = 20
+timestep_size = 0.012
+number_of_timesteps = 1
+plot_timestep_every = 1
+# decide how many timesteps you want analysed. Analysed means, that we write out
+# subsequent errors of the L-iteration within the timestep.
+number_of_timesteps_to_analyse = 1
+starttimes = [0.0]
+# starttimes = [0.0, 0.05]
+
+# starttimes = {
+#     1: 0.0
+#     2: 0.05
+#     4: 0.1
+#     8: 0.2
+#     16: 0.4
+#     32: 0.7
+#     64: 1.0
+#     128: 1.3
+# }
+
+Lw = 0.025 #/timestep_size
+Lnw=Lw
+
+lambda_w = 0
+lambda_nw = 0
+
+include_gravity = False
+debugflag = True
+analyse_condition = False
+
+if mesh_study:
+    output_string = "./output/{}-{}_timesteps{}_P{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree)
+else:
+    for tol in resolutions.values():
+        solver_tol = tol
+    output_string = "./output/{}-{}_timesteps{}_P{}_solver_tol{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree, solver_tol)
+
+# toggle what should be written to files
+if mesh_study:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': True,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+else:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': False,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+
+##### Domain and Interface ####
+# global simulation domain domain
+sub_domain0_vertices = [df.Point(-1.0, -1.0),  #
+                        df.Point(1.0, -1.0),  #
+                        df.Point(1.0, 1.0),  #
+                        df.Point(-1.0, 1.0)]
+
+subdomain0_outer_boundary_verts = {
+    0: [sub_domain0_vertices[0],
+        sub_domain0_vertices[1],
+        sub_domain0_vertices[2],
+        sub_domain0_vertices[3],
+        sub_domain0_vertices[0]]
+}
+
+# list of subdomains given by the boundary polygon vertices.
+# Subdomains are given as a list of dolfin points forming
+# a closed polygon, such that mshr.Polygon(subdomain_def_points[i]) can be used
+# to create the subdomain. subdomain_def_points[0] contains the
+# vertices of the global simulation domain and subdomain_def_points[i] contains the
+# vertices of the subdomain i.
+subdomain_def_points = [sub_domain0_vertices]
+# in the below list, index 0 corresponds to the 12 interface which has index 1
+interface_def_points = None
+
+# if a subdomain has no outer boundary write None instead, i.e.
+# i: None
+# if i is the index of the inner subdomain.
+outer_boundary_def_points = {
+    # subdomain number
+    0 : subdomain0_outer_boundary_verts
+}
+
+# adjacent_subdomains[i] contains the indices of the subdomains sharing the
+# interface i (i.e. given by interface_def_points[i]).
+adjacent_subdomains = None
+isRichards = {
+    0: True, #
+    }
+
+viscosity = {#
+# subdom_num : viscosity
+    0 : {'wetting' :1,
+         'nonwetting': 1}, #
+}
+
+porosity = {#
+# subdom_num : porosity
+    0: 1,#
+}
+
+# Dict of the form: { subdom_num : density }
+densities = {
+    0: {'wetting': 1,  #997,
+        'nonwetting': 1}, #1225}
+}
+
+gravity_acceleration = 9.81
+
+L = {#
+# subdom_num : subdomain L for L-scheme
+    0: {'wetting' :Lw,
+         'nonwetting': Lnw},#
+}
+
+lambda_param = {#
+# subdom_num : lambda parameter for the L-scheme
+    0: {'wetting' :lambda_w,
+         'nonwetting': lambda_nw},#
+}
+
+## relative permeabilty functions on subdomain 1
+def rel_perm1w(s):
+    # relative permeabilty wetting on subdomain1
+    return s**2
+
+def rel_perm1nw(s):
+    # relative permeabilty nonwetting on subdomain1
+    return (1-s)**2
+
+_rel_perm1w = ft.partial(rel_perm1w)
+_rel_perm1nw = ft.partial(rel_perm1nw)
+
+subdomain1_rel_perm = {
+    'wetting': _rel_perm1w,#
+    'nonwetting': _rel_perm1nw
+}
+
+## dictionary of relative permeabilties on all domains.
+relative_permeability = {#
+    0: subdomain1_rel_perm,
+}
+
+# definition of the derivatives of the relative permeabilities
+# relative permeabilty functions on subdomain 1
+def rel_perm1w_prime(s):
+    # relative permeabilty on subdomain1
+    return 2*s
+
+def rel_perm1nw_prime(s):
+    # relative permeabilty on subdomain1
+    return -2*(1-s)
+
+_rel_perm1w_prime = ft.partial(rel_perm1w_prime)
+_rel_perm1nw_prime = ft.partial(rel_perm1nw_prime)
+
+subdomain1_rel_perm_prime = {
+    'wetting': _rel_perm1w_prime,
+    'nonwetting': _rel_perm1nw_prime
+}
+
+# dictionary of relative permeabilties on all domains.
+ka_prime = {
+    0: subdomain1_rel_perm_prime,
+}
+
+
+
+def saturation(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return df.conditional(pc > 0, 1/((1 + pc)**(1/(index + 1))), 1)
+
+def saturation_sym(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return 1/((1 + pc)**(1/(index + 1)))
+
+
+# derivative of S-pc relationship with respect to pc. This is needed for the
+# construction of a analytic solution.
+def saturation_sym_prime(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return -1/((index+1)*(1 + pc)**((index+2)/(index+1)))
+
+
+# def saturation(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pc > 0, -index*pc, 1)
+#
+#
+# def saturation_sym(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index*pc
+#
+#
+# # derivative of S-pc relationship with respect to pc. This is needed for the
+# # construction of a analytic solution.
+# def saturation_sym_prime(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index
+
+
+# note that the conditional definition of S-pc in the nonsymbolic part will be
+# incorporated in the construction of the exact solution below.
+S_pc_sym = {
+    0: ft.partial(saturation_sym, index=1),
+}
+
+S_pc_sym_prime = {
+    0: ft.partial(saturation_sym_prime, index=1),
+}
+
+sat_pressure_relationship = {
+    0: ft.partial(saturation, index=1),
+}
+
+
+#############################################
+# Manufacture source expressions with sympy #
+#############################################
+x, y = sym.symbols('x[0], x[1]')  # needed by UFL
+t = sym.symbols('t', positive=True)
+
+epsilon_x_inner = 0.7
+epsilon_x_outer = 0.99
+epsilon_y_inner = epsilon_x_inner
+epsilon_y_outer = epsilon_x_outer
+
+def mollifier(x, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x/epsilon)**2) + 1)
+    return out_expr
+
+mollifier_handle = ft.partial(mollifier, epsilon=epsilon_x_inner)
+
+pw_sym_x = sym.Piecewise(
+    (mollifier_handle(x), x**2 < epsilon_x_outer**2),
+    (0, True)
+)
+pw_sym_y = sym.Piecewise(
+    (mollifier_handle(y), y**2 < epsilon_y_outer**2),
+    (0, True)
+)
+
+def mollifier2d(x, y, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x**2 + y**2)/epsilon**2) + 1)
+    return out_expr
+
+mollifier2d_handle = ft.partial(mollifier2d, epsilon=epsilon_x_outer)
+
+pw_sym2d_x = sym.Piecewise(
+    (mollifier2d_handle(x, y), x**2 + y**2 < epsilon_x_outer**2),
+    (0, True)
+)
+
+zero_on_epsilon_shrinking_of_subdomain = sym.Piecewise(
+    (mollifier_handle(sym.sqrt(x**2 + y**2)+2*epsilon_x_inner), ((-2*epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<=epsilon_x_inner))),
+    (mollifier_handle(sym.sqrt(x**2 + y**2)-2*epsilon_x_inner), ((epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_x = sym.Piecewise(
+    (mollifier_handle(x+2*epsilon_x_inner), ((-2*epsilon_x_inner<x) & (x<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=x) & (x<=epsilon_x_inner))),
+    (mollifier_handle(x-2*epsilon_x_inner), ((epsilon_x_inner<x) & (x<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_y = sym.Piecewise(
+    (1, y<=-2*epsilon_x_inner),
+    (mollifier_handle(y+2*epsilon_x_inner), ((-2*epsilon_x_inner<y) & (y<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=y) & (y<=epsilon_x_inner))),
+    (mollifier_handle(y-2*epsilon_x_inner), ((epsilon_x_inner<y) & (y<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_shrinking = zero_on_epsilon_shrinking_of_subdomain #zero_on_epsilon_shrinking_of_subdomain_x + zero_on_epsilon_shrinking_of_subdomain_y
+gaussian = pw_sym2d_x# pw_sym_y*pw_sym_x
+cutoff = gaussian/(gaussian + zero_on_shrinking)
+
+# # construction of differentiable characteristic function.
+# def smooth_characteristic_func_on_epsilon_shrinking_of_subdomain0(x, y, epsilon_x_inner, epsilon_y_inner, epsilon_x_outer, epsilon_y_outer):
+#     dist_to_complement_x = ft.partial(mollifier, epsilon=epsilon_x_inner)
+#     dist_to_complement_y = ft.partial(mollifier, epsilon=epsilon_y_inner)
+#     dist_to_complement = dist_to_complement_y(y)*dist_to_complement_x(x)
+#     dist_to_eps_shrinking_x = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_x_outer)
+#     dist_to_eps_shrinking_y = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_y_outer)
+#     dist_to_eps_shrinking = dist_to_eps_shrinking_y(y)*dist_to_eps_shrinking_x(x)
+#     return dist_to_complement/(dist_to_eps_shrinking + dist_to_complement)
+#
+
+# def dist_to_epsilon_thickening_of_subdomain0_complement(x, y, epsilon):
+#     """ calculates the (euklidian distance)^2 of a point x,y to the epsilon
+#         thickening of the complement of the domain.
+#     """
+#     is_inside = ((1-sym.Abs(x) > epsilon) & (1-sym.Abs(y) > epsilon))
+#     sym.Piecewise((0, is_inside))
+
+p_e_sym = {
+    0: {'wetting': (-7 - (1+t*t)*(1 + x*x + y*y)),  #*cutoff,
+        'nonwetting': (-1 -t*(1.1+y + x**2))},  #*cutoff},
+}
+
+pc_e_sym = dict()
+for subdomain, isR in isRichards.items():
+    if isR:
+        pc_e_sym.update({subdomain: -p_e_sym[subdomain]['wetting']})
+    else:
+        pc_e_sym.update({subdomain: p_e_sym[subdomain]['nonwetting']
+                                        - p_e_sym[subdomain]['wetting']})
+
+
+symbols = {"x": x,
+           "y": y,
+           "t": t}
+# turn above symbolic code into exact solution for dolphin and
+# construct the rhs that matches the above exact solution.
+exact_solution_example = hlp.generate_exact_solution_expressions(
+                        symbols=symbols,
+                        isRichards=isRichards,
+                        symbolic_pressure=p_e_sym,
+                        symbolic_capillary_pressure=pc_e_sym,
+                        saturation_pressure_relationship=S_pc_sym,
+                        saturation_pressure_relationship_prime=S_pc_sym_prime,
+                        viscosity=viscosity,
+                        porosity=porosity,
+                        relative_permeability=relative_permeability,
+                        relative_permeability_prime=ka_prime,
+                        densities=densities,
+                        gravity_acceleration=gravity_acceleration,
+                        include_gravity=include_gravity,
+                        )
+source_expression = exact_solution_example['source']
+exact_solution = exact_solution_example['exact_solution']
+initial_condition = exact_solution_example['initial_condition']
+
+# Dictionary of dirichlet boundary conditions.
+dirichletBC = dict()
+# similarly to the outer boundary dictionary, if a patch has no outer boundary
+# None should be written instead of an expression.
+# This is a bit of a brainfuck:
+# dirichletBC[ind] gives a dictionary of the outer boundaries of subdomain ind.
+# Since a domain patch can have several disjoint outer boundary parts, the
+# expressions need to get an enumaration index which starts at 0.
+# So dirichletBC[ind][j] is the dictionary of outer dirichlet conditions of
+# subdomain ind and boundary part j.
+# Finally, dirichletBC[ind][j]['wetting'] and dirichletBC[ind][j]['nonwetting']
+# return the actual expression needed for the dirichlet condition for both
+# phases if present.
+
+# subdomain index: {outer boudary part index: {phase: expression}}
+for subdomain in isRichards.keys():
+    # if subdomain has no outer boundary, outer_boundary_def_points[subdomain] is None
+    if outer_boundary_def_points[subdomain] is None:
+        dirichletBC.update({subdomain: None})
+    else:
+        dirichletBC.update({subdomain: dict()})
+        # set the dirichlet conditions to be the same code as exact solution on
+        # the subdomain.
+        for outer_boundary_ind in outer_boundary_def_points[subdomain].keys():
+            dirichletBC[subdomain].update(
+                {outer_boundary_ind: exact_solution[subdomain]}
+                )
+
+
+# def saturation(pressure, subdomain_index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pressure < 0, 1/((1 - pressure)**(1/(subdomain_index + 1))), 1)
+#
+# sa
+for starttime in starttimes:
+    for mesh_resolution, solver_tol in resolutions.items():
+        # initialise LDD simulation class
+        simulation = ldd.LDDsimulation(
+            tol=1E-14,
+            LDDsolver_tol=solver_tol,
+            debug=debugflag,
+            max_iter_num=max_iter_num,
+            FEM_Lagrange_degree=FEM_Lagrange_degree,
+            mesh_study=mesh_study
+            )
+
+        simulation.set_parameters(use_case=use_case,
+                                  output_dir=output_string,
+                                  subdomain_def_points=subdomain_def_points,
+                                  isRichards=isRichards,
+                                  interface_def_points=interface_def_points,
+                                  outer_boundary_def_points=outer_boundary_def_points,
+                                  adjacent_subdomains=adjacent_subdomains,
+                                  mesh_resolution=mesh_resolution,
+                                  viscosity=viscosity,
+                                  porosity=porosity,
+                                  L=L,
+                                  lambda_param=lambda_param,
+                                  relative_permeability=relative_permeability,
+                                  saturation=sat_pressure_relationship,
+                                  starttime=starttime,
+                                  number_of_timesteps=number_of_timesteps,
+                                  number_of_timesteps_to_analyse=number_of_timesteps_to_analyse,
+                                  plot_timestep_every=plot_timestep_every,
+                                  timestep_size=timestep_size,
+                                  sources=source_expression,
+                                  initial_conditions=initial_condition,
+                                  dirichletBC_expression_strings=dirichletBC,
+                                  exact_solution=exact_solution,
+                                  densities=densities,
+                                  include_gravity=include_gravity,
+                                  write2file=write_to_file,
+                                  )
+
+        simulation.initialise()
+        output_dir = simulation.output_dir
+        # simulation.write_exact_solution_to_xdmf()
+        output = simulation.run(analyse_condition=analyse_condition)
+        for subdomain_index, subdomain_output in output.items():
+            mesh_h = subdomain_output['mesh_size']
+            for phase, different_errornorms in subdomain_output['errornorm'].items():
+                filename = output_dir + "subdomain{}-space-time-errornorm-{}-phase.csv".format(subdomain_index, phase)
+                # for errortype, errornorm in different_errornorms.items():
+
+                    # eocfile = open("eoc_filename", "a")
+                    # eocfile.write( str(mesh_h) + " " + str(errornorm) + "\n" )
+                    # eocfile.close()
+                    # if subdomain.isRichards:mesh_h
+                data_dict = {
+                    'mesh_parameter': mesh_resolution,
+                    'mesh_h': mesh_h,
+                }
+                for error_type, errornorms in different_errornorms.items():
+                    data_dict.update(
+                        {error_type: errornorms}
+                    )
+                errors = pd.DataFrame(data_dict, index=[mesh_resolution])
+                # check if file exists
+                if os.path.isfile(filename) == True:
+                    with open(filename, 'a') as f:
+                        errors.to_csv(f, header=False, sep='\t', encoding='utf-8', index=False)
+                else:
+                    errors.to_csv(filename, sep='\t', encoding='utf-8', index=False)
diff --git a/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/TP-one-patch-mesh-study-fixed-timestep-constant-pressures.py b/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/TP-one-patch-mesh-study-fixed-timestep-constant-pressures.py
new file mode 100755
index 0000000000000000000000000000000000000000..3816aa6041dafdc822e600be7ba2ee2f13e2c3dc
--- /dev/null
+++ b/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/TP-one-patch-mesh-study-fixed-timestep-constant-pressures.py
@@ -0,0 +1,490 @@
+#!/usr/bin/python3
+import dolfin as df
+import mshr
+import numpy as np
+import sympy as sym
+import typing as tp
+import domainPatch as dp
+import LDDsimulation as ldd
+import functools as ft
+import helpers as hlp
+import datetime
+import os
+import pandas as pd
+
+date = datetime.datetime.now()
+datestr = date.strftime("%Y-%m-%d")
+#import ufl as ufl
+
+# init sympy session
+sym.init_printing()
+
+use_case = "TP-one-patch-mesh-study-fixed-timestep-constant-pressures"
+# solver_tol = 5E-9
+max_iter_num = 2000
+FEM_Lagrange_degree = 1
+mesh_study = True
+# resolutions = {128: 1e-7} #[1,2,3,4,5,10,20,40,75,100]
+resolutions = {
+                1: 1e-10,
+                2: 1e-10,
+                4: 1e-10,
+                8: 1e-10,
+                16: 1e-10,
+                32: 1e-10,
+                64: 1e-10,
+                128: 1e-10,
+                256: 1e-10,
+                512: 1e-10,
+                }
+
+############ GRID #######################
+# mesh_resolution = 20
+timestep_size = 0.01
+number_of_timesteps = 1
+plot_timestep_every = 1
+# decide how many timesteps you want analysed. Analysed means, that we write out
+# subsequent errors of the L-iteration within the timestep.
+number_of_timesteps_to_analyse = 1
+starttimes = [0.0, 0.05, 0.1, 0.7, 1.3]
+
+# starttimes = {
+#     1: 0.0
+#     2: 0.05
+#     4: 0.1
+#     8: 0.2
+#     16: 0.4
+#     32: 0.7
+#     64: 1.0
+#     128: 1.3
+# }
+
+Lw = 0.05 #/timestep_size
+Lnw=Lw
+
+lambda_w = 0
+lambda_nw = 0
+
+include_gravity = False
+debugflag = True
+analyse_condition = False
+
+if mesh_study:
+    output_string = "./output/{}-{}_timesteps{}_P{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree)
+else:
+    for tol in resolutions.values():
+        solver_tol = tol
+    output_string = "./output/{}-{}_timesteps{}_P{}_solver_tol{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree, solver_tol)
+
+# toggle what should be written to files
+if mesh_study:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': True,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+else:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': False,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+
+##### Domain and Interface ####
+# global simulation domain domain
+sub_domain0_vertices = [df.Point(-1.0, -1.0),  #
+                        df.Point(1.0, -1.0),  #
+                        df.Point(1.0, 1.0),  #
+                        df.Point(-1.0, 1.0)]
+
+subdomain0_outer_boundary_verts = {
+    0: [sub_domain0_vertices[0],
+        sub_domain0_vertices[1],
+        sub_domain0_vertices[2],
+        sub_domain0_vertices[3],
+        sub_domain0_vertices[0]]
+}
+
+# list of subdomains given by the boundary polygon vertices.
+# Subdomains are given as a list of dolfin points forming
+# a closed polygon, such that mshr.Polygon(subdomain_def_points[i]) can be used
+# to create the subdomain. subdomain_def_points[0] contains the
+# vertices of the global simulation domain and subdomain_def_points[i] contains the
+# vertices of the subdomain i.
+subdomain_def_points = [sub_domain0_vertices]
+# in the below list, index 0 corresponds to the 12 interface which has index 1
+interface_def_points = None
+
+# if a subdomain has no outer boundary write None instead, i.e.
+# i: None
+# if i is the index of the inner subdomain.
+outer_boundary_def_points = {
+    # subdomain number
+    0 : subdomain0_outer_boundary_verts
+}
+
+# adjacent_subdomains[i] contains the indices of the subdomains sharing the
+# interface i (i.e. given by interface_def_points[i]).
+adjacent_subdomains = None
+isRichards = {
+    0: False, #
+    }
+
+viscosity = {#
+# subdom_num : viscosity
+    0 : {'wetting' :1,
+         'nonwetting': 1}, #
+}
+
+porosity = {#
+# subdom_num : porosity
+    0: 1,#
+}
+
+# Dict of the form: { subdom_num : density }
+densities = {
+    0: {'wetting': 1,  #997,
+        'nonwetting': 1}, #1225}
+}
+
+gravity_acceleration = 9.81
+
+L = {#
+# subdom_num : subdomain L for L-scheme
+    0: {'wetting' :Lw,
+         'nonwetting': Lnw},#
+}
+
+lambda_param = {#
+# subdom_num : lambda parameter for the L-scheme
+    0: {'wetting' :lambda_w,
+         'nonwetting': lambda_nw},#
+}
+
+## relative permeabilty functions on subdomain 1
+def rel_perm1w(s):
+    # relative permeabilty wetting on subdomain1
+    return s**2
+
+def rel_perm1nw(s):
+    # relative permeabilty nonwetting on subdomain1
+    return (1-s)**2
+
+_rel_perm1w = ft.partial(rel_perm1w)
+_rel_perm1nw = ft.partial(rel_perm1nw)
+
+subdomain1_rel_perm = {
+    'wetting': _rel_perm1w,#
+    'nonwetting': _rel_perm1nw
+}
+
+## dictionary of relative permeabilties on all domains.
+relative_permeability = {#
+    0: subdomain1_rel_perm,
+}
+
+# definition of the derivatives of the relative permeabilities
+# relative permeabilty functions on subdomain 1
+def rel_perm1w_prime(s):
+    # relative permeabilty on subdomain1
+    return 2*s
+
+def rel_perm1nw_prime(s):
+    # relative permeabilty on subdomain1
+    return -2*(1-s)
+
+_rel_perm1w_prime = ft.partial(rel_perm1w_prime)
+_rel_perm1nw_prime = ft.partial(rel_perm1nw_prime)
+
+subdomain1_rel_perm_prime = {
+    'wetting': _rel_perm1w_prime,
+    'nonwetting': _rel_perm1nw_prime
+}
+
+# dictionary of relative permeabilties on all domains.
+ka_prime = {
+    0: subdomain1_rel_perm_prime,
+}
+
+
+
+def saturation(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return df.conditional(pc > 0, 1/((1 + pc)**(1/(index + 1))), 1)
+
+def saturation_sym(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return 1/((1 + pc)**(1/(index + 1)))
+
+
+# derivative of S-pc relationship with respect to pc. This is needed for the
+# construction of a analytic solution.
+def saturation_sym_prime(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return -1/((index+1)*(1 + pc)**((index+2)/(index+1)))
+
+
+# def saturation(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pc > 0, -index*pc, 1)
+#
+#
+# def saturation_sym(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index*pc
+#
+#
+# # derivative of S-pc relationship with respect to pc. This is needed for the
+# # construction of a analytic solution.
+# def saturation_sym_prime(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index
+
+
+# note that the conditional definition of S-pc in the nonsymbolic part will be
+# incorporated in the construction of the exact solution below.
+S_pc_sym = {
+    0: ft.partial(saturation_sym, index=1),
+}
+
+S_pc_sym_prime = {
+    0: ft.partial(saturation_sym_prime, index=1),
+}
+
+sat_pressure_relationship = {
+    0: ft.partial(saturation, index=1),
+}
+
+
+#############################################
+# Manufacture source expressions with sympy #
+#############################################
+x, y = sym.symbols('x[0], x[1]')  # needed by UFL
+t = sym.symbols('t', positive=True)
+
+epsilon_x_inner = 0.7
+epsilon_x_outer = 0.99
+epsilon_y_inner = epsilon_x_inner
+epsilon_y_outer = epsilon_x_outer
+
+def mollifier(x, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x/epsilon)**2) + 1)
+    return out_expr
+
+mollifier_handle = ft.partial(mollifier, epsilon=epsilon_x_inner)
+
+pw_sym_x = sym.Piecewise(
+    (mollifier_handle(x), x**2 < epsilon_x_outer**2),
+    (0, True)
+)
+pw_sym_y = sym.Piecewise(
+    (mollifier_handle(y), y**2 < epsilon_y_outer**2),
+    (0, True)
+)
+
+def mollifier2d(x, y, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x**2 + y**2)/epsilon**2) + 1)
+    return out_expr
+
+mollifier2d_handle = ft.partial(mollifier2d, epsilon=epsilon_x_outer)
+
+pw_sym2d_x = sym.Piecewise(
+    (mollifier2d_handle(x, y), x**2 + y**2 < epsilon_x_outer**2),
+    (0, True)
+)
+
+zero_on_epsilon_shrinking_of_subdomain = sym.Piecewise(
+    (mollifier_handle(sym.sqrt(x**2 + y**2)+2*epsilon_x_inner), ((-2*epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<=epsilon_x_inner))),
+    (mollifier_handle(sym.sqrt(x**2 + y**2)-2*epsilon_x_inner), ((epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_x = sym.Piecewise(
+    (mollifier_handle(x+2*epsilon_x_inner), ((-2*epsilon_x_inner<x) & (x<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=x) & (x<=epsilon_x_inner))),
+    (mollifier_handle(x-2*epsilon_x_inner), ((epsilon_x_inner<x) & (x<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_y = sym.Piecewise(
+    (1, y<=-2*epsilon_x_inner),
+    (mollifier_handle(y+2*epsilon_x_inner), ((-2*epsilon_x_inner<y) & (y<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=y) & (y<=epsilon_x_inner))),
+    (mollifier_handle(y-2*epsilon_x_inner), ((epsilon_x_inner<y) & (y<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_shrinking = zero_on_epsilon_shrinking_of_subdomain #zero_on_epsilon_shrinking_of_subdomain_x + zero_on_epsilon_shrinking_of_subdomain_y
+gaussian = pw_sym2d_x# pw_sym_y*pw_sym_x
+cutoff = gaussian/(gaussian + zero_on_shrinking)
+
+# # construction of differentiable characteristic function.
+# def smooth_characteristic_func_on_epsilon_shrinking_of_subdomain0(x, y, epsilon_x_inner, epsilon_y_inner, epsilon_x_outer, epsilon_y_outer):
+#     dist_to_complement_x = ft.partial(mollifier, epsilon=epsilon_x_inner)
+#     dist_to_complement_y = ft.partial(mollifier, epsilon=epsilon_y_inner)
+#     dist_to_complement = dist_to_complement_y(y)*dist_to_complement_x(x)
+#     dist_to_eps_shrinking_x = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_x_outer)
+#     dist_to_eps_shrinking_y = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_y_outer)
+#     dist_to_eps_shrinking = dist_to_eps_shrinking_y(y)*dist_to_eps_shrinking_x(x)
+#     return dist_to_complement/(dist_to_eps_shrinking + dist_to_complement)
+#
+
+# def dist_to_epsilon_thickening_of_subdomain0_complement(x, y, epsilon):
+#     """ calculates the (euklidian distance)^2 of a point x,y to the epsilon
+#         thickening of the complement of the domain.
+#     """
+#     is_inside = ((1-sym.Abs(x) > epsilon) & (1-sym.Abs(y) > epsilon))
+#     sym.Piecewise((0, is_inside))
+
+p_e_sym = {
+    0: {'wetting': -3 +0.0*t,  #*cutoff,
+        'nonwetting': -1 +0.0*t},  #*cutoff},
+}
+
+pc_e_sym = dict()
+for subdomain, isR in isRichards.items():
+    if isR:
+        pc_e_sym.update({subdomain: -p_e_sym[subdomain]['wetting']})
+    else:
+        pc_e_sym.update({subdomain: p_e_sym[subdomain]['nonwetting']
+                                        - p_e_sym[subdomain]['wetting']})
+
+
+symbols = {"x": x,
+           "y": y,
+           "t": t}
+# turn above symbolic code into exact solution for dolphin and
+# construct the rhs that matches the above exact solution.
+exact_solution_example = hlp.generate_exact_solution_expressions(
+                        symbols=symbols,
+                        isRichards=isRichards,
+                        symbolic_pressure=p_e_sym,
+                        symbolic_capillary_pressure=pc_e_sym,
+                        saturation_pressure_relationship=S_pc_sym,
+                        saturation_pressure_relationship_prime=S_pc_sym_prime,
+                        viscosity=viscosity,
+                        porosity=porosity,
+                        relative_permeability=relative_permeability,
+                        relative_permeability_prime=ka_prime,
+                        densities=densities,
+                        gravity_acceleration=gravity_acceleration,
+                        include_gravity=include_gravity,
+                        )
+source_expression = exact_solution_example['source']
+exact_solution = exact_solution_example['exact_solution']
+initial_condition = exact_solution_example['initial_condition']
+
+# Dictionary of dirichlet boundary conditions.
+dirichletBC = dict()
+# similarly to the outer boundary dictionary, if a patch has no outer boundary
+# None should be written instead of an expression.
+# This is a bit of a brainfuck:
+# dirichletBC[ind] gives a dictionary of the outer boundaries of subdomain ind.
+# Since a domain patch can have several disjoint outer boundary parts, the
+# expressions need to get an enumaration index which starts at 0.
+# So dirichletBC[ind][j] is the dictionary of outer dirichlet conditions of
+# subdomain ind and boundary part j.
+# Finally, dirichletBC[ind][j]['wetting'] and dirichletBC[ind][j]['nonwetting']
+# return the actual expression needed for the dirichlet condition for both
+# phases if present.
+
+# subdomain index: {outer boudary part index: {phase: expression}}
+for subdomain in isRichards.keys():
+    # if subdomain has no outer boundary, outer_boundary_def_points[subdomain] is None
+    if outer_boundary_def_points[subdomain] is None:
+        dirichletBC.update({subdomain: None})
+    else:
+        dirichletBC.update({subdomain: dict()})
+        # set the dirichlet conditions to be the same code as exact solution on
+        # the subdomain.
+        for outer_boundary_ind in outer_boundary_def_points[subdomain].keys():
+            dirichletBC[subdomain].update(
+                {outer_boundary_ind: exact_solution[subdomain]}
+                )
+
+
+# def saturation(pressure, subdomain_index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pressure < 0, 1/((1 - pressure)**(1/(subdomain_index + 1))), 1)
+#
+# sa
+for starttime in starttimes:
+    for mesh_resolution, solver_tol in resolutions.items():
+        # initialise LDD simulation class
+        simulation = ldd.LDDsimulation(
+            tol=1E-14,
+            LDDsolver_tol=solver_tol,
+            debug=debugflag,
+            max_iter_num=max_iter_num,
+            FEM_Lagrange_degree=FEM_Lagrange_degree,
+            mesh_study=mesh_study
+            )
+
+        simulation.set_parameters(use_case=use_case,
+                                  output_dir=output_string,
+                                  subdomain_def_points=subdomain_def_points,
+                                  isRichards=isRichards,
+                                  interface_def_points=interface_def_points,
+                                  outer_boundary_def_points=outer_boundary_def_points,
+                                  adjacent_subdomains=adjacent_subdomains,
+                                  mesh_resolution=mesh_resolution,
+                                  viscosity=viscosity,
+                                  porosity=porosity,
+                                  L=L,
+                                  lambda_param=lambda_param,
+                                  relative_permeability=relative_permeability,
+                                  saturation=sat_pressure_relationship,
+                                  starttime=starttime,
+                                  number_of_timesteps=number_of_timesteps,
+                                  number_of_timesteps_to_analyse=number_of_timesteps_to_analyse,
+                                  plot_timestep_every=plot_timestep_every,
+                                  timestep_size=timestep_size,
+                                  sources=source_expression,
+                                  initial_conditions=initial_condition,
+                                  dirichletBC_expression_strings=dirichletBC,
+                                  exact_solution=exact_solution,
+                                  densities=densities,
+                                  include_gravity=include_gravity,
+                                  write2file=write_to_file,
+                                  )
+
+        simulation.initialise()
+        output_dir = simulation.output_dir
+        # simulation.write_exact_solution_to_xdmf()
+        output = simulation.run(analyse_condition=analyse_condition)
+        for subdomain_index, subdomain_output in output.items():
+            mesh_h = subdomain_output['mesh_size']
+            for phase, different_errornorms in subdomain_output['errornorm'].items():
+                filename = output_dir + "subdomain{}-space-time-errornorm-{}-phase.csv".format(subdomain_index, phase)
+                # for errortype, errornorm in different_errornorms.items():
+
+                    # eocfile = open("eoc_filename", "a")
+                    # eocfile.write( str(mesh_h) + " " + str(errornorm) + "\n" )
+                    # eocfile.close()
+                    # if subdomain.isRichards:mesh_h
+                data_dict = {
+                    'mesh_parameter': mesh_resolution,
+                    'mesh_h': mesh_h,
+                }
+                for error_type, errornorms in different_errornorms.items():
+                    data_dict.update(
+                        {error_type: errornorms}
+                    )
+                errors = pd.DataFrame(data_dict, index=[mesh_resolution])
+                # check if file exists
+                if os.path.isfile(filename) == True:
+                    with open(filename, 'a') as f:
+                        errors.to_csv(f, header=False, sep='\t', encoding='utf-8', index=False)
+                else:
+                    errors.to_csv(filename, sep='\t', encoding='utf-8', index=False)
diff --git a/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/TP-one-patch-mesh-study-fixed-timestep-nonwetting0.py b/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/TP-one-patch-mesh-study-fixed-timestep-nonwetting0.py
new file mode 100755
index 0000000000000000000000000000000000000000..f15efcf437c5a960dff1b9133ba6c4f36b30f844
--- /dev/null
+++ b/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/TP-one-patch-mesh-study-fixed-timestep-nonwetting0.py
@@ -0,0 +1,491 @@
+#!/usr/bin/python3
+import dolfin as df
+import mshr
+import numpy as np
+import sympy as sym
+import typing as tp
+import domainPatch as dp
+import LDDsimulation as ldd
+import functools as ft
+import helpers as hlp
+import datetime
+import os
+import pandas as pd
+
+date = datetime.datetime.now()
+datestr = date.strftime("%Y-%m-%d")
+#import ufl as ufl
+
+# init sympy session
+sym.init_printing()
+
+use_case = "TP-one-patch-mesh-study-fixed-timestep-nonwetting0"
+# solver_tol = 5E-9
+max_iter_num = 2000
+FEM_Lagrange_degree = 1
+mesh_study = True
+# resolutions = {128: 1e-7} #[1,2,3,4,5,10,20,40,75,100]
+resolutions = {
+                1: 1e-10,
+                2: 1e-10,
+                4: 1e-10,
+                8: 1e-10,
+                16: 1e-10,
+                32: 1e-10,
+                64: 1e-10,
+                128: 1e-10,
+                256: 1e-10,
+                # 512: 1e-10,
+                }
+
+############ GRID #######################
+# mesh_resolution = 20
+timestep_size = 0.01
+number_of_timesteps = 1
+plot_timestep_every = 1
+# decide how many timesteps you want analysed. Analysed means, that we write out
+# subsequent errors of the L-iteration within the timestep.
+number_of_timesteps_to_analyse = 1
+# starttimes = [0.0, 0.05, 0.1, 0.7, 1.3]
+starttimes = [0.7]
+
+# starttimes = {
+#     1: 0.0
+#     2: 0.05
+#     4: 0.1
+#     8: 0.2
+#     16: 0.4
+#     32: 0.7
+#     64: 1.0
+#     128: 1.3
+# }
+
+Lw = 0.05 #/timestep_size
+Lnw=Lw
+
+lambda_w = 0
+lambda_nw = 0
+
+include_gravity = False
+debugflag = True
+analyse_condition = False
+
+if mesh_study:
+    output_string = "./output/{}-{}_timesteps{}_P{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree)
+else:
+    for tol in resolutions.values():
+        solver_tol = tol
+    output_string = "./output/{}-{}_timesteps{}_P{}_solver_tol{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree, solver_tol)
+
+# toggle what should be written to files
+if mesh_study:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': True,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+else:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': False,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+
+##### Domain and Interface ####
+# global simulation domain domain
+sub_domain0_vertices = [df.Point(-1.0, -1.0),  #
+                        df.Point(1.0, -1.0),  #
+                        df.Point(1.0, 1.0),  #
+                        df.Point(-1.0, 1.0)]
+
+subdomain0_outer_boundary_verts = {
+    0: [sub_domain0_vertices[0],
+        sub_domain0_vertices[1],
+        sub_domain0_vertices[2],
+        sub_domain0_vertices[3],
+        sub_domain0_vertices[0]]
+}
+
+# list of subdomains given by the boundary polygon vertices.
+# Subdomains are given as a list of dolfin points forming
+# a closed polygon, such that mshr.Polygon(subdomain_def_points[i]) can be used
+# to create the subdomain. subdomain_def_points[0] contains the
+# vertices of the global simulation domain and subdomain_def_points[i] contains the
+# vertices of the subdomain i.
+subdomain_def_points = [sub_domain0_vertices]
+# in the below list, index 0 corresponds to the 12 interface which has index 1
+interface_def_points = None
+
+# if a subdomain has no outer boundary write None instead, i.e.
+# i: None
+# if i is the index of the inner subdomain.
+outer_boundary_def_points = {
+    # subdomain number
+    0 : subdomain0_outer_boundary_verts
+}
+
+# adjacent_subdomains[i] contains the indices of the subdomains sharing the
+# interface i (i.e. given by interface_def_points[i]).
+adjacent_subdomains = None
+isRichards = {
+    0: False, #
+    }
+
+viscosity = {#
+# subdom_num : viscosity
+    0 : {'wetting' :1,
+         'nonwetting': 1}, #
+}
+
+porosity = {#
+# subdom_num : porosity
+    0: 1,#
+}
+
+# Dict of the form: { subdom_num : density }
+densities = {
+    0: {'wetting': 1,  #997,
+        'nonwetting': 1}, #1225}
+}
+
+gravity_acceleration = 9.81
+
+L = {#
+# subdom_num : subdomain L for L-scheme
+    0: {'wetting' :Lw,
+         'nonwetting': Lnw},#
+}
+
+lambda_param = {#
+# subdom_num : lambda parameter for the L-scheme
+    0: {'wetting' :lambda_w,
+         'nonwetting': lambda_nw},#
+}
+
+## relative permeabilty functions on subdomain 1
+def rel_perm1w(s):
+    # relative permeabilty wetting on subdomain1
+    return s**2
+
+def rel_perm1nw(s):
+    # relative permeabilty nonwetting on subdomain1
+    return (1-s)**2
+
+_rel_perm1w = ft.partial(rel_perm1w)
+_rel_perm1nw = ft.partial(rel_perm1nw)
+
+subdomain1_rel_perm = {
+    'wetting': _rel_perm1w,#
+    'nonwetting': _rel_perm1nw
+}
+
+## dictionary of relative permeabilties on all domains.
+relative_permeability = {#
+    0: subdomain1_rel_perm,
+}
+
+# definition of the derivatives of the relative permeabilities
+# relative permeabilty functions on subdomain 1
+def rel_perm1w_prime(s):
+    # relative permeabilty on subdomain1
+    return 2*s
+
+def rel_perm1nw_prime(s):
+    # relative permeabilty on subdomain1
+    return -2*(1-s)
+
+_rel_perm1w_prime = ft.partial(rel_perm1w_prime)
+_rel_perm1nw_prime = ft.partial(rel_perm1nw_prime)
+
+subdomain1_rel_perm_prime = {
+    'wetting': _rel_perm1w_prime,
+    'nonwetting': _rel_perm1nw_prime
+}
+
+# dictionary of relative permeabilties on all domains.
+ka_prime = {
+    0: subdomain1_rel_perm_prime,
+}
+
+
+
+def saturation(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return df.conditional(pc > 0, 1/((1 + pc)**(1/(index + 1))), 1)
+
+def saturation_sym(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return 1/((1 + pc)**(1/(index + 1)))
+
+
+# derivative of S-pc relationship with respect to pc. This is needed for the
+# construction of a analytic solution.
+def saturation_sym_prime(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return -1/((index+1)*(1 + pc)**((index+2)/(index+1)))
+
+
+# def saturation(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pc > 0, -index*pc, 1)
+#
+#
+# def saturation_sym(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index*pc
+#
+#
+# # derivative of S-pc relationship with respect to pc. This is needed for the
+# # construction of a analytic solution.
+# def saturation_sym_prime(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index
+
+
+# note that the conditional definition of S-pc in the nonsymbolic part will be
+# incorporated in the construction of the exact solution below.
+S_pc_sym = {
+    0: ft.partial(saturation_sym, index=1),
+}
+
+S_pc_sym_prime = {
+    0: ft.partial(saturation_sym_prime, index=1),
+}
+
+sat_pressure_relationship = {
+    0: ft.partial(saturation, index=1),
+}
+
+
+#############################################
+# Manufacture source expressions with sympy #
+#############################################
+x, y = sym.symbols('x[0], x[1]')  # needed by UFL
+t = sym.symbols('t', positive=True)
+
+epsilon_x_inner = 0.7
+epsilon_x_outer = 0.99
+epsilon_y_inner = epsilon_x_inner
+epsilon_y_outer = epsilon_x_outer
+
+def mollifier(x, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x/epsilon)**2) + 1)
+    return out_expr
+
+mollifier_handle = ft.partial(mollifier, epsilon=epsilon_x_inner)
+
+pw_sym_x = sym.Piecewise(
+    (mollifier_handle(x), x**2 < epsilon_x_outer**2),
+    (0, True)
+)
+pw_sym_y = sym.Piecewise(
+    (mollifier_handle(y), y**2 < epsilon_y_outer**2),
+    (0, True)
+)
+
+def mollifier2d(x, y, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x**2 + y**2)/epsilon**2) + 1)
+    return out_expr
+
+mollifier2d_handle = ft.partial(mollifier2d, epsilon=epsilon_x_outer)
+
+pw_sym2d_x = sym.Piecewise(
+    (mollifier2d_handle(x, y), x**2 + y**2 < epsilon_x_outer**2),
+    (0, True)
+)
+
+zero_on_epsilon_shrinking_of_subdomain = sym.Piecewise(
+    (mollifier_handle(sym.sqrt(x**2 + y**2)+2*epsilon_x_inner), ((-2*epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<=epsilon_x_inner))),
+    (mollifier_handle(sym.sqrt(x**2 + y**2)-2*epsilon_x_inner), ((epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_x = sym.Piecewise(
+    (mollifier_handle(x+2*epsilon_x_inner), ((-2*epsilon_x_inner<x) & (x<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=x) & (x<=epsilon_x_inner))),
+    (mollifier_handle(x-2*epsilon_x_inner), ((epsilon_x_inner<x) & (x<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_y = sym.Piecewise(
+    (1, y<=-2*epsilon_x_inner),
+    (mollifier_handle(y+2*epsilon_x_inner), ((-2*epsilon_x_inner<y) & (y<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=y) & (y<=epsilon_x_inner))),
+    (mollifier_handle(y-2*epsilon_x_inner), ((epsilon_x_inner<y) & (y<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_shrinking = zero_on_epsilon_shrinking_of_subdomain #zero_on_epsilon_shrinking_of_subdomain_x + zero_on_epsilon_shrinking_of_subdomain_y
+gaussian = pw_sym2d_x# pw_sym_y*pw_sym_x
+cutoff = gaussian/(gaussian + zero_on_shrinking)
+
+# # construction of differentiable characteristic function.
+# def smooth_characteristic_func_on_epsilon_shrinking_of_subdomain0(x, y, epsilon_x_inner, epsilon_y_inner, epsilon_x_outer, epsilon_y_outer):
+#     dist_to_complement_x = ft.partial(mollifier, epsilon=epsilon_x_inner)
+#     dist_to_complement_y = ft.partial(mollifier, epsilon=epsilon_y_inner)
+#     dist_to_complement = dist_to_complement_y(y)*dist_to_complement_x(x)
+#     dist_to_eps_shrinking_x = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_x_outer)
+#     dist_to_eps_shrinking_y = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_y_outer)
+#     dist_to_eps_shrinking = dist_to_eps_shrinking_y(y)*dist_to_eps_shrinking_x(x)
+#     return dist_to_complement/(dist_to_eps_shrinking + dist_to_complement)
+#
+
+# def dist_to_epsilon_thickening_of_subdomain0_complement(x, y, epsilon):
+#     """ calculates the (euklidian distance)^2 of a point x,y to the epsilon
+#         thickening of the complement of the domain.
+#     """
+#     is_inside = ((1-sym.Abs(x) > epsilon) & (1-sym.Abs(y) > epsilon))
+#     sym.Piecewise((0, is_inside))
+
+p_e_sym = {
+    0: {'wetting': (-7 - (1+t*t)*(1 + x*x + y*y)),  #*cutoff,
+        'nonwetting': 0.0*t},  #*cutoff},
+}
+
+pc_e_sym = dict()
+for subdomain, isR in isRichards.items():
+    if isR:
+        pc_e_sym.update({subdomain: -p_e_sym[subdomain]['wetting']})
+    else:
+        pc_e_sym.update({subdomain: p_e_sym[subdomain]['nonwetting']
+                                        - p_e_sym[subdomain]['wetting']})
+
+
+symbols = {"x": x,
+           "y": y,
+           "t": t}
+# turn above symbolic code into exact solution for dolphin and
+# construct the rhs that matches the above exact solution.
+exact_solution_example = hlp.generate_exact_solution_expressions(
+                        symbols=symbols,
+                        isRichards=isRichards,
+                        symbolic_pressure=p_e_sym,
+                        symbolic_capillary_pressure=pc_e_sym,
+                        saturation_pressure_relationship=S_pc_sym,
+                        saturation_pressure_relationship_prime=S_pc_sym_prime,
+                        viscosity=viscosity,
+                        porosity=porosity,
+                        relative_permeability=relative_permeability,
+                        relative_permeability_prime=ka_prime,
+                        densities=densities,
+                        gravity_acceleration=gravity_acceleration,
+                        include_gravity=include_gravity,
+                        )
+source_expression = exact_solution_example['source']
+exact_solution = exact_solution_example['exact_solution']
+initial_condition = exact_solution_example['initial_condition']
+
+# Dictionary of dirichlet boundary conditions.
+dirichletBC = dict()
+# similarly to the outer boundary dictionary, if a patch has no outer boundary
+# None should be written instead of an expression.
+# This is a bit of a brainfuck:
+# dirichletBC[ind] gives a dictionary of the outer boundaries of subdomain ind.
+# Since a domain patch can have several disjoint outer boundary parts, the
+# expressions need to get an enumaration index which starts at 0.
+# So dirichletBC[ind][j] is the dictionary of outer dirichlet conditions of
+# subdomain ind and boundary part j.
+# Finally, dirichletBC[ind][j]['wetting'] and dirichletBC[ind][j]['nonwetting']
+# return the actual expression needed for the dirichlet condition for both
+# phases if present.
+
+# subdomain index: {outer boudary part index: {phase: expression}}
+for subdomain in isRichards.keys():
+    # if subdomain has no outer boundary, outer_boundary_def_points[subdomain] is None
+    if outer_boundary_def_points[subdomain] is None:
+        dirichletBC.update({subdomain: None})
+    else:
+        dirichletBC.update({subdomain: dict()})
+        # set the dirichlet conditions to be the same code as exact solution on
+        # the subdomain.
+        for outer_boundary_ind in outer_boundary_def_points[subdomain].keys():
+            dirichletBC[subdomain].update(
+                {outer_boundary_ind: exact_solution[subdomain]}
+                )
+
+
+# def saturation(pressure, subdomain_index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pressure < 0, 1/((1 - pressure)**(1/(subdomain_index + 1))), 1)
+#
+# sa
+for starttime in starttimes:
+    for mesh_resolution, solver_tol in resolutions.items():
+        # initialise LDD simulation class
+        simulation = ldd.LDDsimulation(
+            tol=1E-14,
+            LDDsolver_tol=solver_tol,
+            debug=debugflag,
+            max_iter_num=max_iter_num,
+            FEM_Lagrange_degree=FEM_Lagrange_degree,
+            mesh_study=mesh_study
+            )
+
+        simulation.set_parameters(use_case=use_case,
+                                  output_dir=output_string,
+                                  subdomain_def_points=subdomain_def_points,
+                                  isRichards=isRichards,
+                                  interface_def_points=interface_def_points,
+                                  outer_boundary_def_points=outer_boundary_def_points,
+                                  adjacent_subdomains=adjacent_subdomains,
+                                  mesh_resolution=mesh_resolution,
+                                  viscosity=viscosity,
+                                  porosity=porosity,
+                                  L=L,
+                                  lambda_param=lambda_param,
+                                  relative_permeability=relative_permeability,
+                                  saturation=sat_pressure_relationship,
+                                  starttime=starttime,
+                                  number_of_timesteps=number_of_timesteps,
+                                  number_of_timesteps_to_analyse=number_of_timesteps_to_analyse,
+                                  plot_timestep_every=plot_timestep_every,
+                                  timestep_size=timestep_size,
+                                  sources=source_expression,
+                                  initial_conditions=initial_condition,
+                                  dirichletBC_expression_strings=dirichletBC,
+                                  exact_solution=exact_solution,
+                                  densities=densities,
+                                  include_gravity=include_gravity,
+                                  write2file=write_to_file,
+                                  )
+
+        simulation.initialise()
+        output_dir = simulation.output_dir
+        # simulation.write_exact_solution_to_xdmf()
+        output = simulation.run(analyse_condition=analyse_condition)
+        for subdomain_index, subdomain_output in output.items():
+            mesh_h = subdomain_output['mesh_size']
+            for phase, different_errornorms in subdomain_output['errornorm'].items():
+                filename = output_dir + "subdomain{}-space-time-errornorm-{}-phase.csv".format(subdomain_index, phase)
+                # for errortype, errornorm in different_errornorms.items():
+
+                    # eocfile = open("eoc_filename", "a")
+                    # eocfile.write( str(mesh_h) + " " + str(errornorm) + "\n" )
+                    # eocfile.close()
+                    # if subdomain.isRichards:mesh_h
+                data_dict = {
+                    'mesh_parameter': mesh_resolution,
+                    'mesh_h': mesh_h,
+                }
+                for error_type, errornorms in different_errornorms.items():
+                    data_dict.update(
+                        {error_type: errornorms}
+                    )
+                errors = pd.DataFrame(data_dict, index=[mesh_resolution])
+                # check if file exists
+                if os.path.isfile(filename) == True:
+                    with open(filename, 'a') as f:
+                        errors.to_csv(f, header=False, sep='\t', encoding='utf-8', index=False)
+                else:
+                    errors.to_csv(filename, sep='\t', encoding='utf-8', index=False)
diff --git a/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/TP-one-patch-mesh-study-fixed-timestep-wetting0.py b/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/TP-one-patch-mesh-study-fixed-timestep-wetting0.py
new file mode 100755
index 0000000000000000000000000000000000000000..9821788e1557ed8c15233d9efe9b1941cb129e7b
--- /dev/null
+++ b/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/TP-one-patch-mesh-study-fixed-timestep-wetting0.py
@@ -0,0 +1,490 @@
+#!/usr/bin/python3
+import dolfin as df
+import mshr
+import numpy as np
+import sympy as sym
+import typing as tp
+import domainPatch as dp
+import LDDsimulation as ldd
+import functools as ft
+import helpers as hlp
+import datetime
+import os
+import pandas as pd
+
+date = datetime.datetime.now()
+datestr = date.strftime("%Y-%m-%d")
+#import ufl as ufl
+
+# init sympy session
+sym.init_printing()
+
+use_case = "TP-one-patch-mesh-study-fixed-timestep-wetting-constantexi"
+# solver_tol = 5E-9
+max_iter_num = 2000
+FEM_Lagrange_degree = 1
+mesh_study = True
+# resolutions = {128: 1e-7} #[1,2,3,4,5,10,20,40,75,100]
+resolutions = {
+                1: 1e-10,
+                2: 1e-10,
+                4: 1e-10,
+                8: 1e-10,
+                16: 1e-10,
+                32: 1e-10,
+                64: 1e-10,
+                128: 1e-10,
+                256: 1e-10,
+                512: 1e-10,
+                }
+
+############ GRID #######################
+# mesh_resolution = 20
+timestep_size = 0.01
+number_of_timesteps = 1
+plot_timestep_every = 1
+# decide how many timesteps you want analysed. Analysed means, that we write out
+# subsequent errors of the L-iteration within the timestep.
+number_of_timesteps_to_analyse = 1
+starttimes = [0.0, 0.05, 0.1, 0.7, 1.3]
+
+# starttimes = {
+#     1: 0.0
+#     2: 0.05
+#     4: 0.1
+#     8: 0.2
+#     16: 0.4
+#     32: 0.7
+#     64: 1.0
+#     128: 1.3
+# }
+
+Lw = 0.05 #/timestep_size
+Lnw=Lw
+
+lambda_w = 0
+lambda_nw = 0
+
+include_gravity = False
+debugflag = True
+analyse_condition = False
+
+if mesh_study:
+    output_string = "./output/{}-{}_timesteps{}_P{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree)
+else:
+    for tol in resolutions.values():
+        solver_tol = tol
+    output_string = "./output/{}-{}_timesteps{}_P{}_solver_tol{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree, solver_tol)
+
+# toggle what should be written to files
+if mesh_study:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': True,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+else:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': False,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+
+##### Domain and Interface ####
+# global simulation domain domain
+sub_domain0_vertices = [df.Point(-1.0, -1.0),  #
+                        df.Point(1.0, -1.0),  #
+                        df.Point(1.0, 1.0),  #
+                        df.Point(-1.0, 1.0)]
+
+subdomain0_outer_boundary_verts = {
+    0: [sub_domain0_vertices[0],
+        sub_domain0_vertices[1],
+        sub_domain0_vertices[2],
+        sub_domain0_vertices[3],
+        sub_domain0_vertices[0]]
+}
+
+# list of subdomains given by the boundary polygon vertices.
+# Subdomains are given as a list of dolfin points forming
+# a closed polygon, such that mshr.Polygon(subdomain_def_points[i]) can be used
+# to create the subdomain. subdomain_def_points[0] contains the
+# vertices of the global simulation domain and subdomain_def_points[i] contains the
+# vertices of the subdomain i.
+subdomain_def_points = [sub_domain0_vertices]
+# in the below list, index 0 corresponds to the 12 interface which has index 1
+interface_def_points = None
+
+# if a subdomain has no outer boundary write None instead, i.e.
+# i: None
+# if i is the index of the inner subdomain.
+outer_boundary_def_points = {
+    # subdomain number
+    0 : subdomain0_outer_boundary_verts
+}
+
+# adjacent_subdomains[i] contains the indices of the subdomains sharing the
+# interface i (i.e. given by interface_def_points[i]).
+adjacent_subdomains = None
+isRichards = {
+    0: False, #
+    }
+
+viscosity = {#
+# subdom_num : viscosity
+    0 : {'wetting' :1,
+         'nonwetting': 1}, #
+}
+
+porosity = {#
+# subdom_num : porosity
+    0: 1,#
+}
+
+# Dict of the form: { subdom_num : density }
+densities = {
+    0: {'wetting': 1,  #997,
+        'nonwetting': 1}, #1225}
+}
+
+gravity_acceleration = 9.81
+
+L = {#
+# subdom_num : subdomain L for L-scheme
+    0: {'wetting' :Lw,
+         'nonwetting': Lnw},#
+}
+
+lambda_param = {#
+# subdom_num : lambda parameter for the L-scheme
+    0: {'wetting' :lambda_w,
+         'nonwetting': lambda_nw},#
+}
+
+## relative permeabilty functions on subdomain 1
+def rel_perm1w(s):
+    # relative permeabilty wetting on subdomain1
+    return s**2
+
+def rel_perm1nw(s):
+    # relative permeabilty nonwetting on subdomain1
+    return (1-s)**2
+
+_rel_perm1w = ft.partial(rel_perm1w)
+_rel_perm1nw = ft.partial(rel_perm1nw)
+
+subdomain1_rel_perm = {
+    'wetting': _rel_perm1w,#
+    'nonwetting': _rel_perm1nw
+}
+
+## dictionary of relative permeabilties on all domains.
+relative_permeability = {#
+    0: subdomain1_rel_perm,
+}
+
+# definition of the derivatives of the relative permeabilities
+# relative permeabilty functions on subdomain 1
+def rel_perm1w_prime(s):
+    # relative permeabilty on subdomain1
+    return 2*s
+
+def rel_perm1nw_prime(s):
+    # relative permeabilty on subdomain1
+    return -2*(1-s)
+
+_rel_perm1w_prime = ft.partial(rel_perm1w_prime)
+_rel_perm1nw_prime = ft.partial(rel_perm1nw_prime)
+
+subdomain1_rel_perm_prime = {
+    'wetting': _rel_perm1w_prime,
+    'nonwetting': _rel_perm1nw_prime
+}
+
+# dictionary of relative permeabilties on all domains.
+ka_prime = {
+    0: subdomain1_rel_perm_prime,
+}
+
+
+
+def saturation(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return df.conditional(pc > 0, 1/((1 + pc)**(1/(index + 1))), 1)
+
+def saturation_sym(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return 1/((1 + pc)**(1/(index + 1)))
+
+
+# derivative of S-pc relationship with respect to pc. This is needed for the
+# construction of a analytic solution.
+def saturation_sym_prime(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return -1/((index+1)*(1 + pc)**((index+2)/(index+1)))
+
+
+# def saturation(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pc > 0, -index*pc, 1)
+#
+#
+# def saturation_sym(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index*pc
+#
+#
+# # derivative of S-pc relationship with respect to pc. This is needed for the
+# # construction of a analytic solution.
+# def saturation_sym_prime(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index
+
+
+# note that the conditional definition of S-pc in the nonsymbolic part will be
+# incorporated in the construction of the exact solution below.
+S_pc_sym = {
+    0: ft.partial(saturation_sym, index=1),
+}
+
+S_pc_sym_prime = {
+    0: ft.partial(saturation_sym_prime, index=1),
+}
+
+sat_pressure_relationship = {
+    0: ft.partial(saturation, index=1),
+}
+
+
+#############################################
+# Manufacture source expressions with sympy #
+#############################################
+x, y = sym.symbols('x[0], x[1]')  # needed by UFL
+t = sym.symbols('t', positive=True)
+
+epsilon_x_inner = 0.7
+epsilon_x_outer = 0.99
+epsilon_y_inner = epsilon_x_inner
+epsilon_y_outer = epsilon_x_outer
+
+def mollifier(x, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x/epsilon)**2) + 1)
+    return out_expr
+
+mollifier_handle = ft.partial(mollifier, epsilon=epsilon_x_inner)
+
+pw_sym_x = sym.Piecewise(
+    (mollifier_handle(x), x**2 < epsilon_x_outer**2),
+    (0, True)
+)
+pw_sym_y = sym.Piecewise(
+    (mollifier_handle(y), y**2 < epsilon_y_outer**2),
+    (0, True)
+)
+
+def mollifier2d(x, y, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x**2 + y**2)/epsilon**2) + 1)
+    return out_expr
+
+mollifier2d_handle = ft.partial(mollifier2d, epsilon=epsilon_x_outer)
+
+pw_sym2d_x = sym.Piecewise(
+    (mollifier2d_handle(x, y), x**2 + y**2 < epsilon_x_outer**2),
+    (0, True)
+)
+
+zero_on_epsilon_shrinking_of_subdomain = sym.Piecewise(
+    (mollifier_handle(sym.sqrt(x**2 + y**2)+2*epsilon_x_inner), ((-2*epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<=epsilon_x_inner))),
+    (mollifier_handle(sym.sqrt(x**2 + y**2)-2*epsilon_x_inner), ((epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_x = sym.Piecewise(
+    (mollifier_handle(x+2*epsilon_x_inner), ((-2*epsilon_x_inner<x) & (x<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=x) & (x<=epsilon_x_inner))),
+    (mollifier_handle(x-2*epsilon_x_inner), ((epsilon_x_inner<x) & (x<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_y = sym.Piecewise(
+    (1, y<=-2*epsilon_x_inner),
+    (mollifier_handle(y+2*epsilon_x_inner), ((-2*epsilon_x_inner<y) & (y<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=y) & (y<=epsilon_x_inner))),
+    (mollifier_handle(y-2*epsilon_x_inner), ((epsilon_x_inner<y) & (y<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_shrinking = zero_on_epsilon_shrinking_of_subdomain #zero_on_epsilon_shrinking_of_subdomain_x + zero_on_epsilon_shrinking_of_subdomain_y
+gaussian = pw_sym2d_x# pw_sym_y*pw_sym_x
+cutoff = gaussian/(gaussian + zero_on_shrinking)
+
+# # construction of differentiable characteristic function.
+# def smooth_characteristic_func_on_epsilon_shrinking_of_subdomain0(x, y, epsilon_x_inner, epsilon_y_inner, epsilon_x_outer, epsilon_y_outer):
+#     dist_to_complement_x = ft.partial(mollifier, epsilon=epsilon_x_inner)
+#     dist_to_complement_y = ft.partial(mollifier, epsilon=epsilon_y_inner)
+#     dist_to_complement = dist_to_complement_y(y)*dist_to_complement_x(x)
+#     dist_to_eps_shrinking_x = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_x_outer)
+#     dist_to_eps_shrinking_y = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_y_outer)
+#     dist_to_eps_shrinking = dist_to_eps_shrinking_y(y)*dist_to_eps_shrinking_x(x)
+#     return dist_to_complement/(dist_to_eps_shrinking + dist_to_complement)
+#
+
+# def dist_to_epsilon_thickening_of_subdomain0_complement(x, y, epsilon):
+#     """ calculates the (euklidian distance)^2 of a point x,y to the epsilon
+#         thickening of the complement of the domain.
+#     """
+#     is_inside = ((1-sym.Abs(x) > epsilon) & (1-sym.Abs(y) > epsilon))
+#     sym.Piecewise((0, is_inside))
+
+p_e_sym = {
+    0: {'wetting': -10+0*t,  #*cutoff,
+        'nonwetting': (-1 -t*(1.1+y + x**2))},  #*cutoff},
+}
+
+pc_e_sym = dict()
+for subdomain, isR in isRichards.items():
+    if isR:
+        pc_e_sym.update({subdomain: -p_e_sym[subdomain]['wetting']})
+    else:
+        pc_e_sym.update({subdomain: p_e_sym[subdomain]['nonwetting']
+                                        - p_e_sym[subdomain]['wetting']})
+
+
+symbols = {"x": x,
+           "y": y,
+           "t": t}
+# turn above symbolic code into exact solution for dolphin and
+# construct the rhs that matches the above exact solution.
+exact_solution_example = hlp.generate_exact_solution_expressions(
+                        symbols=symbols,
+                        isRichards=isRichards,
+                        symbolic_pressure=p_e_sym,
+                        symbolic_capillary_pressure=pc_e_sym,
+                        saturation_pressure_relationship=S_pc_sym,
+                        saturation_pressure_relationship_prime=S_pc_sym_prime,
+                        viscosity=viscosity,
+                        porosity=porosity,
+                        relative_permeability=relative_permeability,
+                        relative_permeability_prime=ka_prime,
+                        densities=densities,
+                        gravity_acceleration=gravity_acceleration,
+                        include_gravity=include_gravity,
+                        )
+source_expression = exact_solution_example['source']
+exact_solution = exact_solution_example['exact_solution']
+initial_condition = exact_solution_example['initial_condition']
+
+# Dictionary of dirichlet boundary conditions.
+dirichletBC = dict()
+# similarly to the outer boundary dictionary, if a patch has no outer boundary
+# None should be written instead of an expression.
+# This is a bit of a brainfuck:
+# dirichletBC[ind] gives a dictionary of the outer boundaries of subdomain ind.
+# Since a domain patch can have several disjoint outer boundary parts, the
+# expressions need to get an enumaration index which starts at 0.
+# So dirichletBC[ind][j] is the dictionary of outer dirichlet conditions of
+# subdomain ind and boundary part j.
+# Finally, dirichletBC[ind][j]['wetting'] and dirichletBC[ind][j]['nonwetting']
+# return the actual expression needed for the dirichlet condition for both
+# phases if present.
+
+# subdomain index: {outer boudary part index: {phase: expression}}
+for subdomain in isRichards.keys():
+    # if subdomain has no outer boundary, outer_boundary_def_points[subdomain] is None
+    if outer_boundary_def_points[subdomain] is None:
+        dirichletBC.update({subdomain: None})
+    else:
+        dirichletBC.update({subdomain: dict()})
+        # set the dirichlet conditions to be the same code as exact solution on
+        # the subdomain.
+        for outer_boundary_ind in outer_boundary_def_points[subdomain].keys():
+            dirichletBC[subdomain].update(
+                {outer_boundary_ind: exact_solution[subdomain]}
+                )
+
+
+# def saturation(pressure, subdomain_index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pressure < 0, 1/((1 - pressure)**(1/(subdomain_index + 1))), 1)
+#
+# sa
+for starttime in starttimes:
+    for mesh_resolution, solver_tol in resolutions.items():
+        # initialise LDD simulation class
+        simulation = ldd.LDDsimulation(
+            tol=1E-14,
+            LDDsolver_tol=solver_tol,
+            debug=debugflag,
+            max_iter_num=max_iter_num,
+            FEM_Lagrange_degree=FEM_Lagrange_degree,
+            mesh_study=mesh_study
+            )
+
+        simulation.set_parameters(use_case=use_case,
+                                  output_dir=output_string,
+                                  subdomain_def_points=subdomain_def_points,
+                                  isRichards=isRichards,
+                                  interface_def_points=interface_def_points,
+                                  outer_boundary_def_points=outer_boundary_def_points,
+                                  adjacent_subdomains=adjacent_subdomains,
+                                  mesh_resolution=mesh_resolution,
+                                  viscosity=viscosity,
+                                  porosity=porosity,
+                                  L=L,
+                                  lambda_param=lambda_param,
+                                  relative_permeability=relative_permeability,
+                                  saturation=sat_pressure_relationship,
+                                  starttime=starttime,
+                                  number_of_timesteps=number_of_timesteps,
+                                  number_of_timesteps_to_analyse=number_of_timesteps_to_analyse,
+                                  plot_timestep_every=plot_timestep_every,
+                                  timestep_size=timestep_size,
+                                  sources=source_expression,
+                                  initial_conditions=initial_condition,
+                                  dirichletBC_expression_strings=dirichletBC,
+                                  exact_solution=exact_solution,
+                                  densities=densities,
+                                  include_gravity=include_gravity,
+                                  write2file=write_to_file,
+                                  )
+
+        simulation.initialise()
+        output_dir = simulation.output_dir
+        # simulation.write_exact_solution_to_xdmf()
+        output = simulation.run(analyse_condition=analyse_condition)
+        for subdomain_index, subdomain_output in output.items():
+            mesh_h = subdomain_output['mesh_size']
+            for phase, different_errornorms in subdomain_output['errornorm'].items():
+                filename = output_dir + "subdomain{}-space-time-errornorm-{}-phase.csv".format(subdomain_index, phase)
+                # for errortype, errornorm in different_errornorms.items():
+
+                    # eocfile = open("eoc_filename", "a")
+                    # eocfile.write( str(mesh_h) + " " + str(errornorm) + "\n" )
+                    # eocfile.close()
+                    # if subdomain.isRichards:mesh_h
+                data_dict = {
+                    'mesh_parameter': mesh_resolution,
+                    'mesh_h': mesh_h,
+                }
+                for error_type, errornorms in different_errornorms.items():
+                    data_dict.update(
+                        {error_type: errornorms}
+                    )
+                errors = pd.DataFrame(data_dict, index=[mesh_resolution])
+                # check if file exists
+                if os.path.isfile(filename) == True:
+                    with open(filename, 'a') as f:
+                        errors.to_csv(f, header=False, sep='\t', encoding='utf-8', index=False)
+                else:
+                    errors.to_csv(filename, sep='\t', encoding='utf-8', index=False)
diff --git a/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/TP-one-patch-mesh-study-fixed-timestep.py b/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/TP-one-patch-mesh-study-fixed-timestep.py
new file mode 100755
index 0000000000000000000000000000000000000000..e172f97fda09fce04ade6693b1ca2562fc370e44
--- /dev/null
+++ b/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/TP-one-patch-mesh-study-fixed-timestep.py
@@ -0,0 +1,490 @@
+#!/usr/bin/python3
+import dolfin as df
+import mshr
+import numpy as np
+import sympy as sym
+import typing as tp
+import domainPatch as dp
+import LDDsimulation as ldd
+import functools as ft
+import helpers as hlp
+import datetime
+import os
+import pandas as pd
+
+date = datetime.datetime.now()
+datestr = date.strftime("%Y-%m-%d")
+#import ufl as ufl
+
+# init sympy session
+sym.init_printing()
+
+use_case = "TP-one-patch-mesh-study-fixed-timestep"
+# solver_tol = 5E-9
+max_iter_num = 1000
+FEM_Lagrange_degree = 1
+mesh_study = True
+# resolutions = {128: 1e-7} #[1,2,3,4,5,10,20,40,75,100]
+resolutions = {
+                1: 5e-7,
+                2: 5e-7,
+                4: 5e-7,
+                8: 5e-7,
+                16: 5e-7,
+                32: 5e-7,
+                64: 5e-7,
+                128: 5e-7,
+                256: 5e-7,
+                # 512: 1e-10,
+                }
+
+############ GRID #######################
+# mesh_resolution = 20
+timestep_size = 0.0025
+number_of_timesteps = 1
+plot_timestep_every = 1
+# decide how many timesteps you want analysed. Analysed means, that we write out
+# subsequent errors of the L-iteration within the timestep.
+number_of_timesteps_to_analyse = 1
+starttimes = [0.0, 0.05, 0.1, 0.7, 1.3]
+
+# starttimes = {
+#     1: 0.0
+#     2: 0.05
+#     4: 0.1
+#     8: 0.2
+#     16: 0.4
+#     32: 0.7
+#     64: 1.0
+#     128: 1.3
+# }
+
+Lw = 0.025 #/timestep_size
+Lnw=Lw
+
+lambda_w = 0
+lambda_nw = 0
+
+include_gravity = False
+debugflag = False
+analyse_condition = False
+
+if mesh_study:
+    output_string = "./output/{}-{}_timesteps{}_P{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree)
+else:
+    for tol in resolutions.values():
+        solver_tol = tol
+    output_string = "./output/{}-{}_timesteps{}_P{}_solver_tol{}".format(datestr, use_case, number_of_timesteps, FEM_Lagrange_degree, solver_tol)
+
+# toggle what should be written to files
+if mesh_study:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': True,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+else:
+    write_to_file = {
+        'space_errornorms': True,
+        'meshes_and_markers': True,
+        'L_iterations_per_timestep': False,
+        'solutions': True,
+        'absolute_differences': True,
+        'condition_numbers': analyse_condition,
+        'subsequent_errors': True
+    }
+
+##### Domain and Interface ####
+# global simulation domain domain
+sub_domain0_vertices = [df.Point(-1.0, -1.0),  #
+                        df.Point(1.0, -1.0),  #
+                        df.Point(1.0, 1.0),  #
+                        df.Point(-1.0, 1.0)]
+
+subdomain0_outer_boundary_verts = {
+    0: [sub_domain0_vertices[0],
+        sub_domain0_vertices[1],
+        sub_domain0_vertices[2],
+        sub_domain0_vertices[3],
+        sub_domain0_vertices[0]]
+}
+
+# list of subdomains given by the boundary polygon vertices.
+# Subdomains are given as a list of dolfin points forming
+# a closed polygon, such that mshr.Polygon(subdomain_def_points[i]) can be used
+# to create the subdomain. subdomain_def_points[0] contains the
+# vertices of the global simulation domain and subdomain_def_points[i] contains the
+# vertices of the subdomain i.
+subdomain_def_points = [sub_domain0_vertices]
+# in the below list, index 0 corresponds to the 12 interface which has index 1
+interface_def_points = None
+
+# if a subdomain has no outer boundary write None instead, i.e.
+# i: None
+# if i is the index of the inner subdomain.
+outer_boundary_def_points = {
+    # subdomain number
+    0 : subdomain0_outer_boundary_verts
+}
+
+# adjacent_subdomains[i] contains the indices of the subdomains sharing the
+# interface i (i.e. given by interface_def_points[i]).
+adjacent_subdomains = None
+isRichards = {
+    0: False, #
+    }
+
+viscosity = {#
+# subdom_num : viscosity
+    0 : {'wetting' :1,
+         'nonwetting': 1}, #
+}
+
+porosity = {#
+# subdom_num : porosity
+    0: 1,#
+}
+
+# Dict of the form: { subdom_num : density }
+densities = {
+    0: {'wetting': 1,  #997,
+        'nonwetting': 1}, #1225}
+}
+
+gravity_acceleration = 9.81
+
+L = {#
+# subdom_num : subdomain L for L-scheme
+    0: {'wetting' :Lw,
+         'nonwetting': Lnw},#
+}
+
+lambda_param = {#
+# subdom_num : lambda parameter for the L-scheme
+    0: {'wetting' :lambda_w,
+         'nonwetting': lambda_nw},#
+}
+
+## relative permeabilty functions on subdomain 1
+def rel_perm1w(s):
+    # relative permeabilty wetting on subdomain1
+    return s**2
+
+def rel_perm1nw(s):
+    # relative permeabilty nonwetting on subdomain1
+    return (1-s)**2
+
+_rel_perm1w = ft.partial(rel_perm1w)
+_rel_perm1nw = ft.partial(rel_perm1nw)
+
+subdomain1_rel_perm = {
+    'wetting': _rel_perm1w,#
+    'nonwetting': _rel_perm1nw
+}
+
+## dictionary of relative permeabilties on all domains.
+relative_permeability = {#
+    0: subdomain1_rel_perm,
+}
+
+# definition of the derivatives of the relative permeabilities
+# relative permeabilty functions on subdomain 1
+def rel_perm1w_prime(s):
+    # relative permeabilty on subdomain1
+    return 2*s
+
+def rel_perm1nw_prime(s):
+    # relative permeabilty on subdomain1
+    return -2*(1-s)
+
+_rel_perm1w_prime = ft.partial(rel_perm1w_prime)
+_rel_perm1nw_prime = ft.partial(rel_perm1nw_prime)
+
+subdomain1_rel_perm_prime = {
+    'wetting': _rel_perm1w_prime,
+    'nonwetting': _rel_perm1nw_prime
+}
+
+# dictionary of relative permeabilties on all domains.
+ka_prime = {
+    0: subdomain1_rel_perm_prime,
+}
+
+
+
+def saturation(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return df.conditional(pc > 0, 1/((1 + pc)**(1/(index + 1))), 1)
+
+def saturation_sym(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return 1/((1 + pc)**(1/(index + 1)))
+
+
+# derivative of S-pc relationship with respect to pc. This is needed for the
+# construction of a analytic solution.
+def saturation_sym_prime(pc, index):
+    # inverse capillary pressure-saturation-relationship
+    return -1/((index+1)*(1 + pc)**((index+2)/(index+1)))
+
+
+# def saturation(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pc > 0, -index*pc, 1)
+#
+#
+# def saturation_sym(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index*pc
+#
+#
+# # derivative of S-pc relationship with respect to pc. This is needed for the
+# # construction of a analytic solution.
+# def saturation_sym_prime(pc, index):
+#     # inverse capillary pressure-saturation-relationship
+#     return -index
+
+
+# note that the conditional definition of S-pc in the nonsymbolic part will be
+# incorporated in the construction of the exact solution below.
+S_pc_sym = {
+    0: ft.partial(saturation_sym, index=1),
+}
+
+S_pc_sym_prime = {
+    0: ft.partial(saturation_sym_prime, index=1),
+}
+
+sat_pressure_relationship = {
+    0: ft.partial(saturation, index=1),
+}
+
+
+#############################################
+# Manufacture source expressions with sympy #
+#############################################
+x, y = sym.symbols('x[0], x[1]')  # needed by UFL
+t = sym.symbols('t', positive=True)
+
+epsilon_x_inner = 0.7
+epsilon_x_outer = 0.99
+epsilon_y_inner = epsilon_x_inner
+epsilon_y_outer = epsilon_x_outer
+
+def mollifier(x, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x/epsilon)**2) + 1)
+    return out_expr
+
+mollifier_handle = ft.partial(mollifier, epsilon=epsilon_x_inner)
+
+pw_sym_x = sym.Piecewise(
+    (mollifier_handle(x), x**2 < epsilon_x_outer**2),
+    (0, True)
+)
+pw_sym_y = sym.Piecewise(
+    (mollifier_handle(y), y**2 < epsilon_y_outer**2),
+    (0, True)
+)
+
+def mollifier2d(x, y, epsilon):
+    """ one d mollifier """
+    out_expr = sym.exp(-1/(1-(x**2 + y**2)/epsilon**2) + 1)
+    return out_expr
+
+mollifier2d_handle = ft.partial(mollifier2d, epsilon=epsilon_x_outer)
+
+pw_sym2d_x = sym.Piecewise(
+    (mollifier2d_handle(x, y), x**2 + y**2 < epsilon_x_outer**2),
+    (0, True)
+)
+
+zero_on_epsilon_shrinking_of_subdomain = sym.Piecewise(
+    (mollifier_handle(sym.sqrt(x**2 + y**2)+2*epsilon_x_inner), ((-2*epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<=epsilon_x_inner))),
+    (mollifier_handle(sym.sqrt(x**2 + y**2)-2*epsilon_x_inner), ((epsilon_x_inner<sym.sqrt(x**2 + y**2)) & (sym.sqrt(x**2 + y**2)<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_x = sym.Piecewise(
+    (mollifier_handle(x+2*epsilon_x_inner), ((-2*epsilon_x_inner<x) & (x<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=x) & (x<=epsilon_x_inner))),
+    (mollifier_handle(x-2*epsilon_x_inner), ((epsilon_x_inner<x) & (x<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_epsilon_shrinking_of_subdomain_y = sym.Piecewise(
+    (1, y<=-2*epsilon_x_inner),
+    (mollifier_handle(y+2*epsilon_x_inner), ((-2*epsilon_x_inner<y) & (y<-epsilon_x_inner))),
+    (0, ((-epsilon_x_inner<=y) & (y<=epsilon_x_inner))),
+    (mollifier_handle(y-2*epsilon_x_inner), ((epsilon_x_inner<y) & (y<2*epsilon_x_inner))),
+    (1, True),
+)
+
+zero_on_shrinking = zero_on_epsilon_shrinking_of_subdomain #zero_on_epsilon_shrinking_of_subdomain_x + zero_on_epsilon_shrinking_of_subdomain_y
+gaussian = pw_sym2d_x# pw_sym_y*pw_sym_x
+cutoff = gaussian/(gaussian + zero_on_shrinking)
+
+# # construction of differentiable characteristic function.
+# def smooth_characteristic_func_on_epsilon_shrinking_of_subdomain0(x, y, epsilon_x_inner, epsilon_y_inner, epsilon_x_outer, epsilon_y_outer):
+#     dist_to_complement_x = ft.partial(mollifier, epsilon=epsilon_x_inner)
+#     dist_to_complement_y = ft.partial(mollifier, epsilon=epsilon_y_inner)
+#     dist_to_complement = dist_to_complement_y(y)*dist_to_complement_x(x)
+#     dist_to_eps_shrinking_x = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_x_outer)
+#     dist_to_eps_shrinking_y = ft.partial(zero_outside_epsilon_thickening_of_subdomain, epsilon=epsilon_y_outer)
+#     dist_to_eps_shrinking = dist_to_eps_shrinking_y(y)*dist_to_eps_shrinking_x(x)
+#     return dist_to_complement/(dist_to_eps_shrinking + dist_to_complement)
+#
+
+# def dist_to_epsilon_thickening_of_subdomain0_complement(x, y, epsilon):
+#     """ calculates the (euklidian distance)^2 of a point x,y to the epsilon
+#         thickening of the complement of the domain.
+#     """
+#     is_inside = ((1-sym.Abs(x) > epsilon) & (1-sym.Abs(y) > epsilon))
+#     sym.Piecewise((0, is_inside))
+
+p_e_sym = {
+    0: {'wetting': (-7 - (1+t*t)*(1 + x*x + y*y)),  #*cutoff,
+        'nonwetting': (-1 -t*(1.1+y + x**2))},  #*cutoff},
+}
+
+pc_e_sym = dict()
+for subdomain, isR in isRichards.items():
+    if isR:
+        pc_e_sym.update({subdomain: -p_e_sym[subdomain]['wetting']})
+    else:
+        pc_e_sym.update({subdomain: p_e_sym[subdomain]['nonwetting']
+                                        - p_e_sym[subdomain]['wetting']})
+
+
+symbols = {"x": x,
+           "y": y,
+           "t": t}
+# turn above symbolic code into exact solution for dolphin and
+# construct the rhs that matches the above exact solution.
+exact_solution_example = hlp.generate_exact_solution_expressions(
+                        symbols=symbols,
+                        isRichards=isRichards,
+                        symbolic_pressure=p_e_sym,
+                        symbolic_capillary_pressure=pc_e_sym,
+                        saturation_pressure_relationship=S_pc_sym,
+                        saturation_pressure_relationship_prime=S_pc_sym_prime,
+                        viscosity=viscosity,
+                        porosity=porosity,
+                        relative_permeability=relative_permeability,
+                        relative_permeability_prime=ka_prime,
+                        densities=densities,
+                        gravity_acceleration=gravity_acceleration,
+                        include_gravity=include_gravity,
+                        )
+source_expression = exact_solution_example['source']
+exact_solution = exact_solution_example['exact_solution']
+initial_condition = exact_solution_example['initial_condition']
+
+# Dictionary of dirichlet boundary conditions.
+dirichletBC = dict()
+# similarly to the outer boundary dictionary, if a patch has no outer boundary
+# None should be written instead of an expression.
+# This is a bit of a brainfuck:
+# dirichletBC[ind] gives a dictionary of the outer boundaries of subdomain ind.
+# Since a domain patch can have several disjoint outer boundary parts, the
+# expressions need to get an enumaration index which starts at 0.
+# So dirichletBC[ind][j] is the dictionary of outer dirichlet conditions of
+# subdomain ind and boundary part j.
+# Finally, dirichletBC[ind][j]['wetting'] and dirichletBC[ind][j]['nonwetting']
+# return the actual expression needed for the dirichlet condition for both
+# phases if present.
+
+# subdomain index: {outer boudary part index: {phase: expression}}
+for subdomain in isRichards.keys():
+    # if subdomain has no outer boundary, outer_boundary_def_points[subdomain] is None
+    if outer_boundary_def_points[subdomain] is None:
+        dirichletBC.update({subdomain: None})
+    else:
+        dirichletBC.update({subdomain: dict()})
+        # set the dirichlet conditions to be the same code as exact solution on
+        # the subdomain.
+        for outer_boundary_ind in outer_boundary_def_points[subdomain].keys():
+            dirichletBC[subdomain].update(
+                {outer_boundary_ind: exact_solution[subdomain]}
+                )
+
+
+# def saturation(pressure, subdomain_index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pressure < 0, 1/((1 - pressure)**(1/(subdomain_index + 1))), 1)
+#
+# sa
+for starttime in starttimes:
+    for mesh_resolution, solver_tol in resolutions.items():
+        # initialise LDD simulation class
+        simulation = ldd.LDDsimulation(
+            tol=1E-14,
+            LDDsolver_tol=solver_tol,
+            debug=debugflag,
+            max_iter_num=max_iter_num,
+            FEM_Lagrange_degree=FEM_Lagrange_degree,
+            mesh_study=mesh_study
+            )
+
+        simulation.set_parameters(use_case=use_case,
+                                  output_dir=output_string,
+                                  subdomain_def_points=subdomain_def_points,
+                                  isRichards=isRichards,
+                                  interface_def_points=interface_def_points,
+                                  outer_boundary_def_points=outer_boundary_def_points,
+                                  adjacent_subdomains=adjacent_subdomains,
+                                  mesh_resolution=mesh_resolution,
+                                  viscosity=viscosity,
+                                  porosity=porosity,
+                                  L=L,
+                                  lambda_param=lambda_param,
+                                  relative_permeability=relative_permeability,
+                                  saturation=sat_pressure_relationship,
+                                  starttime=starttime,
+                                  number_of_timesteps=number_of_timesteps,
+                                  number_of_timesteps_to_analyse=number_of_timesteps_to_analyse,
+                                  plot_timestep_every=plot_timestep_every,
+                                  timestep_size=timestep_size,
+                                  sources=source_expression,
+                                  initial_conditions=initial_condition,
+                                  dirichletBC_expression_strings=dirichletBC,
+                                  exact_solution=exact_solution,
+                                  densities=densities,
+                                  include_gravity=include_gravity,
+                                  write2file=write_to_file,
+                                  )
+
+        simulation.initialise()
+        output_dir = simulation.output_dir
+        # simulation.write_exact_solution_to_xdmf()
+        output = simulation.run(analyse_condition=analyse_condition)
+        for subdomain_index, subdomain_output in output.items():
+            mesh_h = subdomain_output['mesh_size']
+            for phase, different_errornorms in subdomain_output['errornorm'].items():
+                filename = output_dir + "subdomain{}-space-time-errornorm-{}-phase.csv".format(subdomain_index, phase)
+                # for errortype, errornorm in different_errornorms.items():
+
+                    # eocfile = open("eoc_filename", "a")
+                    # eocfile.write( str(mesh_h) + " " + str(errornorm) + "\n" )
+                    # eocfile.close()
+                    # if subdomain.isRichards:mesh_h
+                data_dict = {
+                    'mesh_parameter': mesh_resolution,
+                    'mesh_h': mesh_h,
+                }
+                for error_type, errornorms in different_errornorms.items():
+                    data_dict.update(
+                        {error_type: errornorms}
+                    )
+                errors = pd.DataFrame(data_dict, index=[mesh_resolution])
+                # check if file exists
+                if os.path.isfile(filename) == True:
+                    with open(filename, 'a') as f:
+                        errors.to_csv(f, header=False, sep='\t', encoding='utf-8', index=False)
+                else:
+                    errors.to_csv(filename, sep='\t', encoding='utf-8', index=False)
diff --git a/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/run-simulation b/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/run-simulation
new file mode 100755
index 0000000000000000000000000000000000000000..0eb497502a082a0fec07a5449b1fe946d59c8cc7
--- /dev/null
+++ b/Two-phase-Two-phase/one-patch/mesh_study_for_fixed_timestep/run-simulation
@@ -0,0 +1,16 @@
+#!/bin/bash
+
+[ $# -eq 0 ] && { echo "Usage: $0 simulation_file [logfile_name]"; exit 1; }
+
+SIMULATION_FILE=$1
+SIMULATION=${SIMULATION_FILE%.py}
+LOGFILE_DEFAULT="$SIMULATION.log"
+
+DATE=$(date -I)
+LOGFILE=${2:-$DATE-$LOGFILE_DEFAULT}
+
+GREETING="Simulation $SIMULATION is run on $DATE by $USER"
+
+echo $GREETING
+echo "running $SIMULATION_FILE | tee $LOGFILE"
+./$SIMULATION_FILE | tee $LOGFILE
diff --git a/Two-phase-Two-phase/one-patch/run-simulation b/Two-phase-Two-phase/one-patch/run-simulation
new file mode 100755
index 0000000000000000000000000000000000000000..0eb497502a082a0fec07a5449b1fe946d59c8cc7
--- /dev/null
+++ b/Two-phase-Two-phase/one-patch/run-simulation
@@ -0,0 +1,16 @@
+#!/bin/bash
+
+[ $# -eq 0 ] && { echo "Usage: $0 simulation_file [logfile_name]"; exit 1; }
+
+SIMULATION_FILE=$1
+SIMULATION=${SIMULATION_FILE%.py}
+LOGFILE_DEFAULT="$SIMULATION.log"
+
+DATE=$(date -I)
+LOGFILE=${2:-$DATE-$LOGFILE_DEFAULT}
+
+GREETING="Simulation $SIMULATION is run on $DATE by $USER"
+
+echo $GREETING
+echo "running $SIMULATION_FILE | tee $LOGFILE"
+./$SIMULATION_FILE | tee $LOGFILE
diff --git a/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case-sinus_solution/TP-TP-2-patch-test_sinus.py b/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case-sinus_solution/TP-TP-2-patch-test_sinus.py
new file mode 100755
index 0000000000000000000000000000000000000000..500b636c624226cd86928fa4f13e2856e2955a68
--- /dev/null
+++ b/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case-sinus_solution/TP-TP-2-patch-test_sinus.py
@@ -0,0 +1,350 @@
+#!/usr/bin/python3
+import dolfin as df
+import mshr
+import numpy as np
+import sympy as sym
+import typing as tp
+import domainPatch as dp
+import LDDsimulation as ldd
+import functools as ft
+#import ufl as ufl
+
+# init sympy session
+sym.init_printing()
+
+##### Domain and Interface ####
+# global simulation domain domain
+sub_domain0_vertices = [df.Point(0.0,0.0), #
+                        df.Point(1.0,0.0),#
+                        df.Point(1.0,1.0),#
+                        df.Point(0.0,1.0)]
+# interface between subdomain1 and subdomain2
+interface12_vertices = [df.Point(0.0, 0.5),
+                        df.Point(1.0, 0.5) ]
+# subdomain1.
+sub_domain1_vertices = [interface12_vertices[0],
+                        interface12_vertices[1],
+                        df.Point(1.0,1.0),
+                        df.Point(0.0,1.0) ]
+
+# vertex coordinates of the outer boundaries. If it can not be specified as a
+# polygon, use an entry per boundary polygon. This information is used for defining
+# the Dirichlet boundary conditions. If a domain is completely internal, the
+# dictionary entry should be 0: None
+subdomain1_outer_boundary_verts = {
+    0: [interface12_vertices[0], #
+        df.Point(0.0,1.0), #
+        df.Point(1.0,1.0), #
+        interface12_vertices[1]]
+}
+# subdomain2
+sub_domain2_vertices = [df.Point(0.0,0.0),
+                        df.Point(1.0,0.0),
+                        interface12_vertices[1],
+                        interface12_vertices[0] ]
+
+subdomain2_outer_boundary_verts = {
+    0: [interface12_vertices[1], #
+        df.Point(1.0,0.0), #
+        df.Point(0.0,0.0), #
+        interface12_vertices[0]]
+}
+# subdomain2_outer_boundary_verts = {
+#     0: [interface12_vertices[0], df.Point(0.0,0.0)],#
+#     1: [df.Point(0.0,0.0), df.Point(1.0,0.0)], #
+#     2: [df.Point(1.0,0.0), interface12_vertices[1]]
+# }
+# subdomain2_outer_boundary_verts = {
+#     0: None
+# }
+
+# list of subdomains given by the boundary polygon vertices.
+# Subdomains are given as a list of dolfin points forming
+# a closed polygon, such that mshr.Polygon(subdomain_def_points[i]) can be used
+# to create the subdomain. subdomain_def_points[0] contains the
+# vertices of the global simulation domain and subdomain_def_points[i] contains the
+# vertices of the subdomain i.
+subdomain_def_points = [sub_domain0_vertices,#
+                      sub_domain1_vertices,#
+                      sub_domain2_vertices]
+# in the below list, index 0 corresponds to the 12 interface which has index 1
+interface_def_points = [interface12_vertices]
+
+# if a subdomain has no outer boundary write None instead, i.e.
+# i: None
+# if i is the index of the inner subdomain.
+outer_boundary_def_points = {
+    # subdomain number
+    1 : subdomain1_outer_boundary_verts,
+    2 : subdomain2_outer_boundary_verts
+}
+
+# adjacent_subdomains[i] contains the indices of the subdomains sharing the
+# interface i (i.e. given by interface_def_points[i]).
+adjacent_subdomains = [[1,2]]
+isRichards = {
+    1: False, #
+    2: False
+    }
+
+
+############ GRID ########################ü
+mesh_resolution = 35
+timestep_size = 1*0.0001
+number_of_timesteps = 500
+# decide how many timesteps you want analysed. Analysed means, that we write out
+# subsequent errors of the L-iteration within the timestep.
+number_of_timesteps_to_analyse = 11
+starttime = 0
+
+viscosity = {#
+# subdom_num : viscosity
+    1 : {'wetting' :1,
+         'nonwetting': 1/50}, #
+    2 : {'wetting' :1,
+         'nonwetting': 1/50}
+}
+
+porosity = {#
+# subdom_num : porosity
+    1 : 1,#
+    2 : 1
+}
+
+L = {#
+# subdom_num : subdomain L for L-scheme
+    1 : {'wetting' :0.6,
+         'nonwetting': 0.6},#
+    2 : {'wetting' :0.6,
+         'nonwetting': 0.6}
+}
+
+lambda_param = {#
+# subdom_num : lambda parameter for the L-scheme
+    1 : {'wetting' :600,
+         'nonwetting': 1500},#
+    2 : {'wetting' :600,
+         'nonwetting': 1500}
+}
+
+## relative permeabilty functions on subdomain 1
+def rel_perm1w(s):
+    # relative permeabilty wetting on subdomain1
+    return s**2
+
+def rel_perm1nw(s):
+    # relative permeabilty nonwetting on subdomain1
+    return (1-s)**2
+
+_rel_perm1w = ft.partial(rel_perm1w)
+_rel_perm1nw = ft.partial(rel_perm1nw)
+subdomain1_rel_perm = {
+    'wetting': _rel_perm1w,#
+    'nonwetting': _rel_perm1nw
+}
+## relative permeabilty functions on subdomain 2
+def rel_perm2w(s):
+    # relative permeabilty wetting on subdomain2
+    return s**2
+def rel_perm2nw(s):
+    # relative permeabilty nonwetting on subdomain2
+    return (1-s)**2
+
+_rel_perm2w = ft.partial(rel_perm2w)
+_rel_perm2nw = ft.partial(rel_perm2nw)
+
+subdomain2_rel_perm = {
+    'wetting': _rel_perm2w,#
+    'nonwetting': _rel_perm2nw
+}
+
+## dictionary of relative permeabilties on all domains.
+relative_permeability = {#
+    1: subdomain1_rel_perm,
+    2: subdomain2_rel_perm
+}
+
+# S-pc-relation ship. We use the van Genuchten approach, i.e. pc = 1/alpha*(S^{-1/m} -1)^1/n, where
+# we set alpha = 0, assume m = 1-1/n (see Helmig) and assume that residual saturation is Sw
+def saturation(capillary_pressure, n_index, alpha):
+    # inverse capillary pressure-saturation-relationship
+    return df.conditional(capillary_pressure > 0, 1/((1 + (alpha*capillary_pressure)**n_index)**((n_index - 1)/n_index)), 1)
+
+# S-pc-relation ship. We use the van Genuchten approach, i.e. pc = 1/alpha*(S^{-1/m} -1)^1/n, where
+# we set alpha = 0, assume m = 1-1/n (see Helmig) and assume that residual saturation is Sw
+def saturation_sym(capillary_pressure, n_index, alpha):
+    # inverse capillary pressure-saturation-relationship
+    #df.conditional(capillary_pressure > 0,
+    return 1/((1 + (alpha*capillary_pressure)**n_index)**((n_index - 1)/n_index))
+
+S_pc_rel = {#
+    1: ft.partial(saturation_sym, n_index = 6, alpha=0.001),# n= 3 stands for non-uniform porous media
+    2: ft.partial(saturation_sym, n_index = 6, alpha=0.001) # n=6 stands for uniform porous media matrix (siehe Helmig)
+}
+
+S_pc_rel_sym = {#
+    1: ft.partial(saturation_sym, n_index = sym.Symbol('n'), alpha = sym.Symbol('a')),# n= 3 stands for non-uniform porous media
+    2: ft.partial(saturation_sym, n_index = sym.Symbol('n'), alpha = sym.Symbol('a')) # n=6 stands for uniform porous media matrix (siehe Helmig)
+}
+
+#### Manufacture source expressions with sympy
+###############################################################################
+## subdomain1
+x, y = sym.symbols('x[0], x[1]') # needed by UFL
+t = sym.symbols('t', positive=True)
+#f = -sym.diff(u, x, 2) - sym.diff(u, y, 2)  # -Laplace(u)
+#f = sym.simplify(f)                         # simplify f
+p1_w = -4 - 3*sym.sin(-2*t+2*x)*sym.sin(1/2*y-1.2*t)
+p1_nw = -10 - 6*sym.sin(x-1*t)*sym.sin(-0.5*t + y)
+
+#dtS1_w = sym.diff(S_pc_rel_sym[1](p1_nw - p1_w), t, 1)
+#dtS1_nw = -sym.diff(S_pc_rel_sym[1](p1_nw - p1_w), t, 1)
+dtS1_w = porosity[1]*sym.diff(S_pc_rel[1](p1_nw - p1_w), t, 1)
+dtS1_nw = -porosity[1]*sym.diff(S_pc_rel[1](p1_nw - p1_w), t, 1)
+print("dtS1_w = ", dtS1_w, "\n")
+print("dtS1_nw = ", dtS1_nw, "\n")
+
+#dxdxflux1_w = -sym.diff(relative_permeability[1]['wetting'](S_pc_rel_sym[1](p1_nw - p1_w))*sym.diff(p1_w, x, 1), x, 1)
+#dydyflux1_w = -sym.diff(relative_permeability[1]['wetting'](S_pc_rel_sym[1](p1_nw - p1_w))*sym.diff(p1_w, y, 1), y, 1)
+dxdxflux1_w = -1/viscosity[1]['wetting']*sym.diff(relative_permeability[1]['wetting'](S_pc_rel[1](p1_nw - p1_w))*sym.diff(p1_w, x, 1), x, 1)
+dydyflux1_w = -1/viscosity[1]['wetting']*sym.diff(relative_permeability[1]['wetting'](S_pc_rel[1](p1_nw - p1_w))*sym.diff(p1_w, y, 1), y, 1)
+
+rhs1_w = dtS1_w + dxdxflux1_w + dydyflux1_w
+rhs1_w = sym.printing.ccode(rhs1_w)
+print("rhs_w = ", rhs1_w, "\n")
+#rhs_w = sym.expand(rhs_w)
+#print("rhs_w", rhs_w, "\n")
+#rhs_w = sym.collect(rhs_w, x)
+#print("rhs_w", rhs_w, "\n")
+
+#dxdxflux1_nw = -sym.diff(relative_permeability[1]['nonwetting'](S_pc_rel_sym[1](p1_nw - p1_w))*sym.diff(p1_nw, x, 1), x, 1)
+#dydyflux1_nw = -sym.diff(relative_permeability[1]['nonwetting'](S_pc_rel_sym[1](p1_nw - p1_w))*sym.diff(p1_nw, y, 1), y, 1)
+dxdxflux1_nw = -1/viscosity[1]['nonwetting']*sym.diff(relative_permeability[1]['nonwetting'](1-S_pc_rel[1](p1_nw - p1_w))*sym.diff(p1_nw, x, 1), x, 1)
+dydyflux1_nw = -1/viscosity[1]['nonwetting']*sym.diff(relative_permeability[1]['nonwetting'](1-S_pc_rel[1](p1_nw - p1_w))*sym.diff(p1_nw, y, 1), y, 1)
+
+rhs1_nw = dtS1_nw + dxdxflux1_nw + dydyflux1_nw
+rhs1_nw = sym.printing.ccode(rhs1_nw)
+print("rhs_nw = ", rhs1_nw, "\n")
+
+## subdomain2
+p2_w = -4 - 3*sym.sin(-2*t+2*x)*sym.sin(1/2*y-1.2*t)
+p2_nw = -10 - 6*sym.sin(x-1*t)*sym.sin(-0.5*t + y)
+
+
+
+#dtS2_w = sym.diff(S_pc_rel_sym[2](p2_nw - p2_w), t, 1)
+#dtS2_nw = -sym.diff(S_pc_rel_sym[2](p2_nw - p2_w), t, 1)
+dtS2_w = porosity[2]*sym.diff(S_pc_rel[2](p2_nw - p2_w), t, 1)
+dtS2_nw = -porosity[2]*sym.diff(S_pc_rel[2](p2_nw - p2_w), t, 1)
+print("dtS2_w = ", dtS2_w, "\n")
+print("dtS2_nw = ", dtS2_nw, "\n")
+
+#dxdxflux2_w = -sym.diff(relative_permeability[2]['wetting'](S_pc_rel_sym[2](p2_nw - p2_w))*sym.diff(p2_w, x, 1), x, 1)
+#dydyflux2_w = -sym.diff(relative_permeability[2]['wetting'](S_pc_rel_sym[2](p2_nw - p2_w))*sym.diff(p2_w, y, 1), y, 1)
+dxdxflux2_w = -1/viscosity[2]['wetting']*sym.diff(relative_permeability[2]['wetting'](S_pc_rel[2](p2_nw - p2_w))*sym.diff(p2_w, x, 1), x, 1)
+dydyflux2_w = -1/viscosity[2]['wetting']*sym.diff(relative_permeability[2]['wetting'](S_pc_rel[2](p2_nw - p2_w))*sym.diff(p2_w, y, 1), y, 1)
+
+rhs2_w = dtS2_w + dxdxflux2_w + dydyflux2_w
+rhs2_w = sym.printing.ccode(rhs2_w)
+print("rhs2_w = ", rhs2_w, "\n")
+#rhs_w = sym.expand(rhs_w)
+#print("rhs_w", rhs_w, "\n")
+#rhs_w = sym.collect(rhs_w, x)
+#print("rhs_w", rhs_w, "\n")
+
+#dxdxflux2_nw = -sym.diff(relative_permeability[2]['nonwetting'](S_pc_rel_sym[2](p2_nw - p2_w))*sym.diff(p2_nw, x, 1), x, 1)
+#dydyflux2_nw = -sym.diff(relative_permeability[2]['nonwetting'](S_pc_rel_sym[2](p2_nw - p2_w))*sym.diff(p2_nw, y, 1), y, 1)
+dxdxflux2_nw = -1/viscosity[2]['nonwetting']*sym.diff(relative_permeability[2]['nonwetting'](1-S_pc_rel[2](p2_nw - p2_w))*sym.diff(p2_nw, x, 1), x, 1)
+dydyflux2_nw = -1/viscosity[2]['nonwetting']*sym.diff(relative_permeability[2]['nonwetting'](1-S_pc_rel[2](p2_nw - p2_w))*sym.diff(p2_nw, y, 1), y, 1)
+
+rhs2_nw = dtS2_nw + dxdxflux2_nw + dydyflux2_nw
+rhs2_nw = sym.printing.ccode(rhs2_nw)
+print("rhs2_nw = ", rhs2_nw, "\n")
+
+
+###############################################################################
+
+source_expression = {
+    1: {'wetting': rhs1_w,
+        'nonwetting': rhs1_nw},
+    2: {'wetting': rhs2_w,
+        'nonwetting': rhs2_nw}
+}
+
+p1_w_00 = p1_w.subs(t, 0)
+p1_nw_00 = p1_nw.subs(t, 0)
+p2_w_00 = p2_w.subs(t, 0)
+p2_nw_00 = p2_nw.subs(t, 0)
+# p1_w_00 = sym.printing.ccode(p1_w_00)
+
+initial_condition = {
+    1: {'wetting': sym.printing.ccode(p1_w_00),
+        'nonwetting': sym.printing.ccode(p1_nw_00)},#
+    2: {'wetting': sym.printing.ccode(p2_w_00),
+        'nonwetting': sym.printing.ccode(p2_nw_00)}
+}
+
+exact_solution = {
+    1: {'wetting': sym.printing.ccode(p1_w),
+        'nonwetting': sym.printing.ccode(p1_nw)},#
+    2: {'wetting': sym.printing.ccode(p2_w),
+        'nonwetting': sym.printing.ccode(p2_nw)}
+}
+
+# similary to the outer boundary dictionary, if a patch has no outer boundary
+# None should be written instead of an expression. This is a bit of a brainfuck:
+# dirichletBC[ind] gives a dictionary of the outer boundaries of subdomain ind.
+# Since a domain patch can have several disjoint outer boundary parts, the expressions
+# need to get an enumaration index which starts at 0. So dirichletBC[ind][j] is
+# the dictionary of outer dirichlet conditions of subdomain ind and boundary part j.
+# finally, dirichletBC[ind][j]['wetting'] and dirichletBC[ind][j]['nonwetting'] return
+# the actual expression needed for the dirichlet condition for both phases if present.
+dirichletBC = {
+#subdomain index: {outer boudary part index: {phase: expression}}
+    1: { 0: {'wetting': sym.printing.ccode(p1_w),
+             'nonwetting': sym.printing.ccode(p1_nw)}},
+    2: { 0: {'wetting': sym.printing.ccode(p2_w),
+             'nonwetting': sym.printing.ccode(p2_nw)}}
+}
+
+# def saturation(pressure, subdomain_index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pressure < 0, 1/((1 - pressure)**(1/(subdomain_index + 1))), 1)
+#
+# sa
+
+write_to_file = {
+    'meshes_and_markers': True,
+    'L_iterations': True
+}
+
+
+# initialise LDD simulation class
+simulation = ldd.LDDsimulation(tol = 1E-14, debug = False, LDDsolver_tol=1E-6)
+simulation.set_parameters(output_dir = "./output/",#
+    subdomain_def_points = subdomain_def_points,#
+    isRichards = isRichards,#
+    interface_def_points = interface_def_points,#
+    outer_boundary_def_points = outer_boundary_def_points,#
+    adjacent_subdomains = adjacent_subdomains,#
+    mesh_resolution = mesh_resolution,#
+    viscosity = viscosity,#
+    porosity = porosity,#
+    L = L,#
+    lambda_param = lambda_param,#
+    relative_permeability = relative_permeability,#
+    saturation = S_pc_rel,#
+    starttime = starttime,#
+    number_of_timesteps = number_of_timesteps,
+    number_of_timesteps_to_analyse = number_of_timesteps_to_analyse,
+    timestep_size = timestep_size,#
+    sources = source_expression,#
+    initial_conditions = initial_condition,#
+    dirichletBC_expression_strings = dirichletBC,#
+    exact_solution = exact_solution,#
+    write2file = write_to_file,#
+    )
+
+simulation.initialise()
+# simulation.write_exact_solution_to_xdmf()
+simulation.run()
diff --git a/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case-sinus_solution/startup.sh b/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case-sinus_solution/startup.sh
new file mode 120000
index 0000000000000000000000000000000000000000..e845a35044d6c2295b0bbf425f94f815da87e858
--- /dev/null
+++ b/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case-sinus_solution/startup.sh
@@ -0,0 +1 @@
+../Jupyter_Notebook_Setup/startup.sh
\ No newline at end of file
diff --git a/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case/startup.sh b/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case/startup.sh
new file mode 100755
index 0000000000000000000000000000000000000000..2dce5dcce065f5cb67d57d34a01d88b59d6abcf5
--- /dev/null
+++ b/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case/startup.sh
@@ -0,0 +1,3 @@
+#!/bin/bash
+source ../.env/bin/activate
+jupyter notebook
diff --git a/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case_sanitycheck/TP-TP-2-patch-test_sanity-check.py b/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case_sanitycheck/TP-TP-2-patch-test_sanity-check.py
new file mode 100755
index 0000000000000000000000000000000000000000..b6d89ef6dc9de492689348456f299e321ab5b9f2
--- /dev/null
+++ b/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case_sanitycheck/TP-TP-2-patch-test_sanity-check.py
@@ -0,0 +1,350 @@
+#!/usr/bin/python3
+import dolfin as df
+import mshr
+import numpy as np
+import sympy as sym
+import typing as tp
+import domainPatch as dp
+import LDDsimulation as ldd
+import functools as ft
+#import ufl as ufl
+
+# init sympy session
+sym.init_printing()
+
+##### Domain and Interface ####
+# global simulation domain domain
+sub_domain0_vertices = [df.Point(0.0,0.0), #
+                        df.Point(1.0,0.0),#
+                        df.Point(1.0,1.0),#
+                        df.Point(0.0,1.0)]
+# interface between subdomain1 and subdomain2
+interface12_vertices = [df.Point(0.0, 0.5),
+                        df.Point(1.0, 0.5) ]
+# subdomain1.
+sub_domain1_vertices = [interface12_vertices[0],
+                        interface12_vertices[1],
+                        df.Point(1.0,1.0),
+                        df.Point(0.0,1.0) ]
+
+# vertex coordinates of the outer boundaries. If it can not be specified as a
+# polygon, use an entry per boundary polygon. This information is used for defining
+# the Dirichlet boundary conditions. If a domain is completely internal, the
+# dictionary entry should be 0: None
+subdomain1_outer_boundary_verts = {
+    0: [interface12_vertices[0], #
+        df.Point(0.0,1.0), #
+        df.Point(1.0,1.0), #
+        interface12_vertices[1]]
+}
+# subdomain2
+sub_domain2_vertices = [df.Point(0.0,0.0),
+                        df.Point(1.0,0.0),
+                        interface12_vertices[1],
+                        interface12_vertices[0] ]
+
+subdomain2_outer_boundary_verts = {
+    0: [interface12_vertices[1], #
+        df.Point(1.0,0.0), #
+        df.Point(0.0,0.0), #
+        interface12_vertices[0]]
+}
+# subdomain2_outer_boundary_verts = {
+#     0: [interface12_vertices[0], df.Point(0.0,0.0)],#
+#     1: [df.Point(0.0,0.0), df.Point(1.0,0.0)], #
+#     2: [df.Point(1.0,0.0), interface12_vertices[1]]
+# }
+# subdomain2_outer_boundary_verts = {
+#     0: None
+# }
+
+# list of subdomains given by the boundary polygon vertices.
+# Subdomains are given as a list of dolfin points forming
+# a closed polygon, such that mshr.Polygon(subdomain_def_points[i]) can be used
+# to create the subdomain. subdomain_def_points[0] contains the
+# vertices of the global simulation domain and subdomain_def_points[i] contains the
+# vertices of the subdomain i.
+subdomain_def_points = [sub_domain0_vertices,#
+                      sub_domain1_vertices,#
+                      sub_domain2_vertices]
+# in the below list, index 0 corresponds to the 12 interface which has index 1
+interface_def_points = [interface12_vertices]
+
+# if a subdomain has no outer boundary write None instead, i.e.
+# i: None
+# if i is the index of the inner subdomain.
+outer_boundary_def_points = {
+    # subdomain number
+    1 : subdomain1_outer_boundary_verts,
+    2 : subdomain2_outer_boundary_verts
+}
+
+# adjacent_subdomains[i] contains the indices of the subdomains sharing the
+# interface i (i.e. given by interface_def_points[i]).
+adjacent_subdomains = [[1,2]]
+isRichards = {
+    1: False, #
+    2: False
+    }
+
+
+############ GRID ########################ü
+mesh_resolution = 20
+timestep_size = 1*0.001
+number_of_timesteps = 20
+# decide how many timesteps you want analysed. Analysed means, that we write out
+# subsequent errors of the L-iteration within the timestep.
+number_of_timesteps_to_analyse = 11
+starttime = 0
+
+viscosity = {#
+# subdom_num : viscosity
+    1 : {'wetting' :1,
+         'nonwetting': 1/50}, #
+    2 : {'wetting' :1,
+         'nonwetting': 1/50}
+}
+
+porosity = {#
+# subdom_num : porosity
+    1 : 1,#
+    2 : 1
+}
+
+L = {#
+# subdom_num : subdomain L for L-scheme
+    1 : {'wetting' :0.25,
+         'nonwetting': 0.25},#
+    2 : {'wetting' :0.25,
+         'nonwetting': 0.25}
+}
+
+lambda_param = {#
+# subdom_num : lambda parameter for the L-scheme
+    1 : {'wetting' :140,
+         'nonwetting': 2400},#
+    2 : {'wetting' :140,
+         'nonwetting': 2400}
+}
+
+## relative permeabilty functions on subdomain 1
+def rel_perm1w(s):
+    # relative permeabilty wetting on subdomain1
+    return s**2
+
+def rel_perm1nw(s):
+    # relative permeabilty nonwetting on subdomain1
+    return (1-s)**2
+
+_rel_perm1w = ft.partial(rel_perm1w)
+_rel_perm1nw = ft.partial(rel_perm1nw)
+subdomain1_rel_perm = {
+    'wetting': _rel_perm1w,#
+    'nonwetting': _rel_perm1nw
+}
+## relative permeabilty functions on subdomain 2
+def rel_perm2w(s):
+    # relative permeabilty wetting on subdomain2
+    return s**2
+def rel_perm2nw(s):
+    # relative permeabilty nonwetting on subdomain2
+    return (1-s)**2
+
+_rel_perm2w = ft.partial(rel_perm2w)
+_rel_perm2nw = ft.partial(rel_perm2nw)
+
+subdomain2_rel_perm = {
+    'wetting': _rel_perm2w,#
+    'nonwetting': _rel_perm2nw
+}
+
+## dictionary of relative permeabilties on all domains.
+relative_permeability = {#
+    1: subdomain1_rel_perm,
+    2: subdomain2_rel_perm
+}
+
+# S-pc-relation ship. We use the van Genuchten approach, i.e. pc = 1/alpha*(S^{-1/m} -1)^1/n, where
+# we set alpha = 0, assume m = 1-1/n (see Helmig) and assume that residual saturation is Sw
+def saturation(capillary_pressure, n_index, alpha):
+    # inverse capillary pressure-saturation-relationship
+    return df.conditional(capillary_pressure > 0, 1/((1 + (alpha*capillary_pressure)**n_index)**((n_index - 1)/n_index)), 1)
+
+# S-pc-relation ship. We use the van Genuchten approach, i.e. pc = 1/alpha*(S^{-1/m} -1)^1/n, where
+# we set alpha = 0, assume m = 1-1/n (see Helmig) and assume that residual saturation is Sw
+def saturation_sym(capillary_pressure, n_index, alpha):
+    # inverse capillary pressure-saturation-relationship
+    #df.conditional(capillary_pressure > 0,
+    return 1/((1 + (alpha*capillary_pressure)**n_index)**((n_index - 1)/n_index))
+
+S_pc_rel = {#
+    1: ft.partial(saturation_sym, n_index = 3, alpha=0.001),# n= 3 stands for non-uniform porous media
+    2: ft.partial(saturation_sym, n_index = 3, alpha=0.001) # n=6 stands for uniform porous media matrix (siehe Helmig)
+}
+
+S_pc_rel_sym = {#
+    1: ft.partial(saturation_sym, n_index = sym.Symbol('n'), alpha = sym.Symbol('a')),# n= 3 stands for non-uniform porous media
+    2: ft.partial(saturation_sym, n_index = sym.Symbol('n'), alpha = sym.Symbol('a')) # n=6 stands for uniform porous media matrix (siehe Helmig)
+}
+
+#### Manufacture source expressions with sympy
+###############################################################################
+## subdomain1
+x, y = sym.symbols('x[0], x[1]') # needed by UFL
+t = sym.symbols('t', positive=True)
+#f = -sym.diff(u, x, 2) - sym.diff(u, y, 2)  # -Laplace(u)
+#f = sym.simplify(f)                         # simplify f
+p1_w = -20 - (1+t*t)*(1 + x**2 + (y-0.5)**2)
+p1_nw = -t*(1-(y-0.5) + x**2)**2 - sym.sqrt(2+t**2)*(1 + (y-0.5)**2 + x**2)
+
+
+#dtS1_w = sym.diff(S_pc_rel_sym[1](p1_nw - p1_w), t, 1)
+#dtS1_nw = -sym.diff(S_pc_rel_sym[1](p1_nw - p1_w), t, 1)
+dtS1_w = porosity[1]*sym.diff(S_pc_rel[1](p1_nw - p1_w), t, 1)
+dtS1_nw = -porosity[1]*sym.diff(S_pc_rel[1](p1_nw - p1_w), t, 1)
+print("dtS1_w = ", dtS1_w, "\n")
+print("dtS1_nw = ", dtS1_nw, "\n")
+
+#dxdxflux1_w = -sym.diff(relative_permeability[1]['wetting'](S_pc_rel_sym[1](p1_nw - p1_w))*sym.diff(p1_w, x, 1), x, 1)
+#dydyflux1_w = -sym.diff(relative_permeability[1]['wetting'](S_pc_rel_sym[1](p1_nw - p1_w))*sym.diff(p1_w, y, 1), y, 1)
+dxdxflux1_w = -1/viscosity[1]['wetting']*sym.diff(relative_permeability[1]['wetting'](S_pc_rel[1](p1_nw - p1_w))*sym.diff(p1_w, x, 1), x, 1)
+dydyflux1_w = -1/viscosity[1]['wetting']*sym.diff(relative_permeability[1]['wetting'](S_pc_rel[1](p1_nw - p1_w))*sym.diff(p1_w, y, 1), y, 1)
+
+rhs1_w = dtS1_w + dxdxflux1_w + dydyflux1_w
+rhs1_w = sym.printing.ccode(rhs1_w)
+print("rhs_w = ", rhs1_w, "\n")
+#rhs_w = sym.expand(rhs_w)
+#print("rhs_w", rhs_w, "\n")
+#rhs_w = sym.collect(rhs_w, x)
+#print("rhs_w", rhs_w, "\n")
+
+#dxdxflux1_nw = -sym.diff(relative_permeability[1]['nonwetting'](S_pc_rel_sym[1](p1_nw - p1_w))*sym.diff(p1_nw, x, 1), x, 1)
+#dydyflux1_nw = -sym.diff(relative_permeability[1]['nonwetting'](S_pc_rel_sym[1](p1_nw - p1_w))*sym.diff(p1_nw, y, 1), y, 1)
+dxdxflux1_nw = -1/viscosity[1]['nonwetting']*sym.diff(relative_permeability[1]['nonwetting'](1-S_pc_rel[1](p1_nw - p1_w))*sym.diff(p1_nw, x, 1), x, 1)
+dydyflux1_nw = -1/viscosity[1]['nonwetting']*sym.diff(relative_permeability[1]['nonwetting'](1-S_pc_rel[1](p1_nw - p1_w))*sym.diff(p1_nw, y, 1), y, 1)
+
+rhs1_nw = dtS1_nw + dxdxflux1_nw + dydyflux1_nw
+rhs1_nw = sym.printing.ccode(rhs1_nw)
+print("rhs_nw = ", rhs1_nw, "\n")
+
+## subdomain2
+p2_w = -20 - (1+t*t)*(1 + x**2)
+p2_nw = -t*(1 + x**2)**2 - sym.sqrt(2+t**2)*(1 + x**2)
+
+
+#dtS2_w = sym.diff(S_pc_rel_sym[2](p2_nw - p2_w), t, 1)
+#dtS2_nw = -sym.diff(S_pc_rel_sym[2](p2_nw - p2_w), t, 1)
+dtS2_w = porosity[2]*sym.diff(S_pc_rel[2](p2_nw - p2_w), t, 1)
+dtS2_nw = -porosity[2]*sym.diff(S_pc_rel[2](p2_nw - p2_w), t, 1)
+print("dtS2_w = ", dtS2_w, "\n")
+print("dtS2_nw = ", dtS2_nw, "\n")
+
+#dxdxflux2_w = -sym.diff(relative_permeability[2]['wetting'](S_pc_rel_sym[2](p2_nw - p2_w))*sym.diff(p2_w, x, 1), x, 1)
+#dydyflux2_w = -sym.diff(relative_permeability[2]['wetting'](S_pc_rel_sym[2](p2_nw - p2_w))*sym.diff(p2_w, y, 1), y, 1)
+dxdxflux2_w = -1/viscosity[2]['wetting']*sym.diff(relative_permeability[2]['wetting'](S_pc_rel[2](p2_nw - p2_w))*sym.diff(p2_w, x, 1), x, 1)
+dydyflux2_w = -1/viscosity[2]['wetting']*sym.diff(relative_permeability[2]['wetting'](S_pc_rel[2](p2_nw - p2_w))*sym.diff(p2_w, y, 1), y, 1)
+
+rhs2_w = dtS2_w + dxdxflux2_w + dydyflux2_w
+rhs2_w = sym.printing.ccode(rhs2_w)
+print("rhs2_w = ", rhs2_w, "\n")
+#rhs_w = sym.expand(rhs_w)
+#print("rhs_w", rhs_w, "\n")
+#rhs_w = sym.collect(rhs_w, x)
+#print("rhs_w", rhs_w, "\n")
+
+#dxdxflux2_nw = -sym.diff(relative_permeability[2]['nonwetting'](S_pc_rel_sym[2](p2_nw - p2_w))*sym.diff(p2_nw, x, 1), x, 1)
+#dydyflux2_nw = -sym.diff(relative_permeability[2]['nonwetting'](S_pc_rel_sym[2](p2_nw - p2_w))*sym.diff(p2_nw, y, 1), y, 1)
+dxdxflux2_nw = -1/viscosity[2]['nonwetting']*sym.diff(relative_permeability[2]['nonwetting'](1-S_pc_rel[2](p2_nw - p2_w))*sym.diff(p2_nw, x, 1), x, 1)
+dydyflux2_nw = -1/viscosity[2]['nonwetting']*sym.diff(relative_permeability[2]['nonwetting'](1-S_pc_rel[2](p2_nw - p2_w))*sym.diff(p2_nw, y, 1), y, 1)
+
+rhs2_nw = dtS2_nw + dxdxflux2_nw + dydyflux2_nw
+rhs2_nw = sym.printing.ccode(rhs2_nw)
+print("rhs2_nw = ", rhs2_nw, "\n")
+
+
+###############################################################################
+
+source_expression = {
+    1: {'wetting': rhs1_w,
+        'nonwetting': rhs1_nw},
+    2: {'wetting': rhs2_w,
+        'nonwetting': rhs2_nw}
+}
+
+p1_w_00 = p1_w.subs(t, 0)
+p1_nw_00 = p1_nw.subs(t, 0)
+p2_w_00 = p2_w.subs(t, 0)
+p2_nw_00 = p2_nw.subs(t, 0)
+# p1_w_00 = sym.printing.ccode(p1_w_00)
+
+initial_condition = {
+    1: {'wetting': sym.printing.ccode(p1_w_00),
+        'nonwetting': sym.printing.ccode(p1_nw_00)},#
+    2: {'wetting': sym.printing.ccode(p2_w_00),
+        'nonwetting': sym.printing.ccode(p2_nw_00)}
+}
+
+exact_solution = {
+    1: {'wetting': sym.printing.ccode(p1_w),
+        'nonwetting': sym.printing.ccode(p1_nw)},#
+    2: {'wetting': sym.printing.ccode(p2_w),
+        'nonwetting': sym.printing.ccode(p2_nw)}
+}
+
+# similary to the outer boundary dictionary, if a patch has no outer boundary
+# None should be written instead of an expression. This is a bit of a brainfuck:
+# dirichletBC[ind] gives a dictionary of the outer boundaries of subdomain ind.
+# Since a domain patch can have several disjoint outer boundary parts, the expressions
+# need to get an enumaration index which starts at 0. So dirichletBC[ind][j] is
+# the dictionary of outer dirichlet conditions of subdomain ind and boundary part j.
+# finally, dirichletBC[ind][j]['wetting'] and dirichletBC[ind][j]['nonwetting'] return
+# the actual expression needed for the dirichlet condition for both phases if present.
+dirichletBC = {
+#subdomain index: {outer boudary part index: {phase: expression}}
+    1: { 0: {'wetting': sym.printing.ccode(p1_w),
+             'nonwetting': sym.printing.ccode(p1_nw)}},
+    2: { 0: {'wetting': sym.printing.ccode(p2_w),
+             'nonwetting': sym.printing.ccode(p2_nw)}}
+}
+
+# def saturation(pressure, subdomain_index):
+#     # inverse capillary pressure-saturation-relationship
+#     return df.conditional(pressure < 0, 1/((1 - pressure)**(1/(subdomain_index + 1))), 1)
+#
+# sa
+
+write_to_file = {
+    'meshes_and_markers': True,
+    'L_iterations': True
+}
+
+
+# initialise LDD simulation class
+simulation = ldd.LDDsimulation(tol = 1E-14)
+simulation.set_parameters(output_dir = "./output/",#
+    subdomain_def_points = subdomain_def_points,#
+    isRichards = isRichards,#
+    interface_def_points = interface_def_points,#
+    outer_boundary_def_points = outer_boundary_def_points,#
+    adjacent_subdomains = adjacent_subdomains,#
+    mesh_resolution = mesh_resolution,#
+    viscosity = viscosity,#
+    porosity = porosity,#
+    L = L,#
+    lambda_param = lambda_param,#
+    relative_permeability = relative_permeability,#
+    saturation = S_pc_rel,#
+    starttime = starttime,#
+    number_of_timesteps = number_of_timesteps,
+    number_of_timesteps_to_analyse = number_of_timesteps_to_analyse,
+    timestep_size = timestep_size,#
+    sources = source_expression,#
+    initial_conditions = initial_condition,#
+    dirichletBC_expression_strings = dirichletBC,#
+    exact_solution = exact_solution,#
+    write2file = write_to_file,#
+    )
+
+simulation.initialise()
+# simulation.write_exact_solution_to_xdmf()
+simulation.run()
diff --git a/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case_sanitycheck/startup.sh b/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case_sanitycheck/startup.sh
new file mode 120000
index 0000000000000000000000000000000000000000..e845a35044d6c2295b0bbf425f94f815da87e858
--- /dev/null
+++ b/Two-phase-Two-phase/two-patch/archive/TP-TP-patch-test-case_sanitycheck/startup.sh
@@ -0,0 +1 @@
+../Jupyter_Notebook_Setup/startup.sh
\ No newline at end of file