Re: [Libmesh-users] Proper way of imposing Weak Dirichlet boundary condition

[Roy S. <roy...@ic...>]

On Thu, 19 Mar 2015, Zhang wrote:

> Another question is :Does the DirichletBoundary class also uses
> nodewise assignment implicitly?

DirichletBoundary calculates constraints by first doing interpolation
at nodes, then (in 2D and 3D) projection on edges holding nodal dof
coefficients fixed, then (in 3D) projection on faces holding nodal and
edge dof coefficients fixed.

If you set incompatible constraints on different boundary sides that
share the same node or edge (e.g. a lid-driven cavity problem) then
which constraint is applied depends on which constraint you added to
the system first.  The *earliest* added constraint takes precedence.
---
Roy