Modeling heterogeneous material expansion with mixed elements

[dokken]

For the boundar conditions, please consider

How to impose spatially varying dirichletbc boundary conditions for one direction in a linear elasticity problem?

This is because the last keyword argument V is only used when you collapse a function into a sub space. Then you send in two arguments in locate_dofs_topological, then uncollapsed and collapsed subspace. This returns you two arrays of degrees of freedom in each of these spaces. Since the collapsed function has no direct relationship to its parent object, one supplied the subspace to ensure that the BCs are imposed on the correct part of the variational form

and/or

Boundary condition to single direction in the subspace of Mixed function space

You are taking the first sub-space of the mixed element, which is V, not V.sub(0) You can check this by printing ME.element.num_sub_elements, which gives you 5, not 6. Thus, you would have to change: To ME0y, _ = ME.sub(0).sub(1).collapse() bottom_value2 = fem.Function(ME0y) bottom_value2.x.array[:]= 0 right_corner_vertex = mesh.locate_entities_boundary(msh,0,right_corner) right_dof = fem.locate_dofs_topological ((ME.sub(0).sub(1),ME0y),0,right_corner_vertex) bc_right_corner = fem.dirichl…

as well as
https://jsdokken.com/dolfinx-tutorial/chapter3/component_bc.html
and
https://docs.fenicsproject.org/dolfinx/v0.8.0/python/demos/demo_stokes.html#non-blocked-direct-solver