When a boundary condition is enforced using Pointwise constraints or
Weak constraints, it may come into conflict with boundary conditions at adjacent boundaries. When this happens, you can use the
Excluded Edges or
Excluded Points sections (collapsed by default) to exclude affected edges or points from one of the boundary conditions. This ensure that the other, remaining, condition prevails.
If the boundary condition is enforced using Pointwise constraints, then no constraint is added at the constraint points that belong to the excluded entities. When using
Weak constraints, the Lagrange multiplier variable will be constrained on the excluded entities, which effectively removes the constraint. Since the
Nitsche method is implemented as a distributed contribution on the boundary, it cannot be disabled locally at edges or points. The
Excluded Edges or
Excluded Points sections are therefore not available when this method is used.
The mesh displacement is prescribed using a pointwise constraint at Lagrange points of the same order as the geometry representation. The default Constraint method is
Elemental, which means that constraints are applied for each Lagrange point in each element separately; if the constraint is discontinuous between elements, there will be multiple separate constraints at shared points. When using the alternative
Nodal constraints the constraint expression is first averaged over all elements sharing a constraint point, before applying a single constraint.
By default, the Constraint type is set to
Automatic, which generally is interpreted as pointwise constraints for deformation conditions and weak constraints for velocity conditions.