boundary condition labeling

[krober10nd]

• Boundaries should be able to be labeled for application of solver-specific boundary conditions.
• For example, edges/facets on top-most boundary get X integer label.

[krober10nd]

• This is just an example for the future. Labels all boundary edges with a y-coordinate > 0 with a tag 11.

 import numpy as np
 
 import meshio
 import SeismicMesh
 
 bbox = (0.0, 1.0, 0.0, 1.0)
 square = SeismicMesh.Rectangle(bbox)
 points, cells = SeismicMesh.generate_mesh(domain=square, edge_length=0.20)
 
 # This gets the edges of the mesh in a winding order.
 ordered_bnde = SeismicMesh.geometry.get_winded_boundary_edges(cells)
 mdpt = points[ordered_bnde].sum(1) / 2
 sel = ordered_bnde[mdpt[:, 1] > 0, :]
 
 # Write to gmsh22 format with boundary conditions
 meshio.write_points_cells(
     "example.msh",
     points,
     cells=[
         ("triangle", cells),
         ("line", np.array(sel)),
     ],
     field_data={
         "Edges": np.array([11, 1]),
     },
     cell_data={
         "gmsh:physical": [
             np.repeat(3, len(cells)),
             np.repeat(11, len(sel)),
         ],
         "gmsh:geometrical": [
             np.repeat(1, len(cells)),
             np.repeat(1, len(sel)),
         ],
     },
     file_format="gmsh22",
     binary=False,
 )