revert most of the interpolates

LDDsimulation/LDDsimulation.py

@@ -1052,7 +1052,7 @@ class LDDsimulation(object):
                     f_expr = subdomain.source[phase]
                     f_expr.t = timestep
                     source.update(
-                        {phase: df.interpolate(
+                        {phase: df.project(
                             f_expr, subdomain.function_space["pressure"][phase]
                             )
                         }
@@ -1092,7 +1092,7 @@ class LDDsimulation(object):
                         exact_capillary_pressure.vector().set_local(pc_temp)
                     exact_capillary_pressure.rename("pc_exact", "pc_exact")
                     file.write(exact_capillary_pressure, timestep)
-                    saturation_w = df.interpolate(
+                    saturation_w = df.project(
                         S(exact_capillary_pressure),
                         subdomain.function_space["pressure"]["wetting"]
                         )
@@ -1100,7 +1100,7 @@ class LDDsimulation(object):
                     saturation_w.rename("Sw_exact", "Sw_exact")
                     file.write(saturation_w, timestep)
                     # S_nw = 1-S(exact_capillary_pressure).vector().get_local()
-                    saturation_nw = df.interpolate(
+                    saturation_nw = df.project(
                         1-S(exact_capillary_pressure),
                         subdomain.function_space["pressure"]["wetting"]
                         )