Hierarhical mesh

mesh
1

Hello everyone,

I have an interest in building of a time-dependent phase-field solver with the possibility of mesh adaptivity. I want to ask if there are some examples in the usage of

When constructor of HierarchicalMesh is called following Error occurs:
AttributeError: module ‘dolfin.cpp.mesh’ has no attribute ‘MeshHierarchy’

My code:
from fenics import *
import dolfin.cpp

mesh = RectangleMesh(Point(0,0),Point(L,L),N_el,N_el)
Mesh_H = dolfin.cpp.mesh.MeshHierarchy(mesh)

2

This work by Alexander Zimmerman might be of your interest: https://github.com/alexanderzimmerman/phaseflow-fenics

3

Thank you for the answer. If i have right understood, in this solver they use remeshing for mesh coarsening, which is not the best solution. In opposite MeshHierarchy class posses method coarsen().

4

If you look in the source code, the “coarsen()” method does exactly the same.

// Set up refinement markers to re-refine the parent mesh
MeshFunction edge_markers(parent_mesh, 1, false);
const std::map<std::size_t, std::size_t>& edge_to_vertex
= *(_relation->edge_to_global_vertex);

// Find edges which were previously refined, but now only mark them
// if not a parent of a “coarsening” vertex
for (EdgeIterator e(*parent_mesh); !e.end(); ++e)
{
auto edge_it = edge_to_vertex.find(e->index());
if (edge_it != edge_to_vertex.end())
{
// Previously refined edge: find child vertex
const std::size_t child_vertex_global_index = edge_it->second;
if (coarsening_vertices.find(child_vertex_global_index)
== coarsening_vertices.end())
{
// Not a “coarsening” vertex, so mark edge for refinement
edge_markers[*e] = true;
}
}
}