Minor formating of contact mechanics modules

src/porepy/models/contact_mechanics_biot_model.py

@@ -3,10 +3,12 @@
 
 The domain $[0, 2]\times[0, 1]$ with six fractures. We do not consider any fluid, and
 solve only for the linear elasticity coupled to the contact
+
+NOTE: This module should be considered an experimental feature, which will likely
+undergo major changes (or be deleted).
+
 """
 import numpy as np
-import scipy.sparse as sps
-from scipy.spatial.distance import cdist
 import porepy as pp
 
 from porepy.utils import assign_discretizations

src/porepy/models/contact_mechanics_model.py

@@ -4,10 +4,15 @@
 The setup handles parameters, variables and discretizations. Default (unitary-like)
 parameters are set. A "run script" function for setting up the class and solving the
 nonlinear contact mechanics problem is also provided.
+
+NOTE: This module should be considered an experimental feature, which will likely
+undergo major changes (or be deleted).
+
 """
 import numpy as np
 import scipy.sparse as sps
 from scipy.spatial.distance import cdist
+
 import porepy as pp
 
 
@@ -43,6 +48,7 @@ def create_grid(self):
             gb (pp.GridBucket): The produced grid bucket.
             Nd (int): The dimension of the matrix, i.e., the highest dimension in the
                 grid bucket.
+                
         """
         # List the fracture points
         self.frac_pts = np.array([[0.2, 0.8], [0.5, 0.5]])
@@ -261,6 +267,7 @@ def extract_iterate(self, assembler, solution_vector):
 
         Returns:
             (np.array): displacement solution vector for the Nd grid.
+            
         """
         dof = np.cumsum(np.append(0, np.asarray(assembler.full_dof)))
 

src/porepy/numerics/interface_laws/contact_mechanics_interface_laws.py

@@ -398,13 +398,18 @@ class MatrixScalarToForceBalance:
 
     We account for the grad P contribution to the forces on the higher-dimensional
     internal boundary, i.e. the last term of:
+
         boundary_traction_hat = stress * u_hat + bound_stress * u_mortar + gradP * p_hat
+
     Note that with this approach to discretization of the boundary pressure force, it
     will only be included for nonzero values of the biot_alpha coefficient.
 
     If the scalar is e.g. pressure, subtraction of the pressure contribution is needed:
+
         \lambda_contact - p_check I \dot n = boundary_traction_hat
+
     This is taken care of by FracturePressureToForceBalance.
+
     """
 
     def __init__(self, keyword, discr_master, discr_slave):
@@ -542,6 +547,7 @@ class FractureScalarToForceBalance:
 
     For the contact mechanics, we only want to consider the _contact_ traction. Thus, we
     have to subtract the pressure contribution, i.e.
+    
         \lambda_contact - p_check I \dot n = boundary_traction_hat,
 
     since the full tractions experienced by a fracture surface are the sum of the