How to calculate the optimized size of mesh?

[dokken]

There are several things you can consider:

1. Check if you get the analytical solution for the first time step.
2. Check if the solution changes by using a structured mesh (like BoxMesh(Point(0,0,0), Point(40,40,40),N,N,N))
3. Check if the solution changes by increasing the degree of the finite element function space.

You should also note that the error can be related to using the point source. See the other post I helped you out with:

Setting Delta-function-like initial condition

Consider: from dolfin import * p = Point(0.41, 0.42, 0) mesh = UnitSquareMesh(10,10) tree = mesh.bounding_box_tree() # Find which cell point is located in cell, distance = tree.compute_closest_entity(p) vertices = mesh.cells()[cell] V = FunctionSpace(mesh, "CG", 1) # Find the closest vertex in the cell vertex_coordinates = mesh.coordinates()[vertices] dist = 1e3 closest = None for i, v in enumerate(vertex_coordinates): p_ = Point(v) dist_ = p.distance(p_) print(v) if dist_ <…