explain material parameters

Usecases/README.md

@@ -278,12 +278,15 @@ In this block you only need to change the line
 ~~~
 substructuring = dss.twoSoilLayers()
 ~~~
+to change the substructuring.
 This block calls constructors of substructurings. These are classes defined in
 `../LDDsimulation/domainSubstructuring.py`.
 If you want to define your own substructurings have a look in that file.
 Some explantion is given in that file on how to define substructuring classes.
 
 ### MODEL CONFIGURATION
+The model configuration block sets all model parameters: Which model is assumed, material parameters, relative permeabilties, pc-S relationships etc.
+lets look at the first part:
 ~~~python
 # MODEL CONFIGURATION #########################################################
 isRichards = {
@@ -326,11 +329,28 @@ L = {#
 
 
 lambda_param = {#
-# subdom_num : lambda parameter for the L-scheme
+# interface_index : lambda parameter for the L-scheme
     0 : {'wetting' :lambda_w,
          'nonwetting': lambda_nw},#
 }
+~~~
+All the dictionaries except for `lambda_param` use the subodomain index as
+key. In `lambda_param` the index corresponds to the number of the interface.  These indices are defined by the substructuring sourced in `substructuring = dss.twoSoilLayers()` so that needs to fit. If there is a missmatch, the code
+might through an error.
+In detail:
+- `isRichards`: toggle between the models. If set to `True` Richards model is
+assumed, when set to `False`, the two-phase model.
+- `viscosity`: Set the viscosity on each subdomain.
+- `porosity`: Set the porosity on each subdomain.
+- `densities`: Set the densities on each subdomain.
+- `gravity_acceleration`: Set the gravity acceleration on each subdomain.
+- `L`: Set the L parametrs on each subdomain. This gets filled with the information of `### LDD SCHEME PARAMETERS` block.
+- `lambda_param`: Set the λ parameters for each interface. Again this gets filled with the information of `### LDD SCHEME PARAMETERS` block.
+
+The relative permeabilities and pc-S relationships are set subsequently in
+the block:
  
+~~~python
 intrinsic_permeability = {
     1: 0.01,
     2: 0.01,

Usecases/Two-phase-Richards/two-patch/TP-R-two-patch-test-case/TP-R-2-patch-test.py

@@ -191,7 +191,7 @@ L = {#
 
 
 lambda_param = {#
-# subdom_num : lambda parameter for the L-scheme
+# interface_index : lambda parameter for the L-scheme
     0 : {'wetting' :lambda_w,
          'nonwetting': lambda_nw},#
 }