Slip Dirichlet Boundary Conditions

Although they might be satisfied at the start of a time step, general slip Dirichlet boundary conditions (DBC) present unique challenges. Unlike the sticky DBCs, they cannot be directly addressed using the DOF elimination method, primarily because their constraint Jacobian does not consist of identity matrix blocks. To navigate this complexity, we can adopt a change-of-basis strategy.

Before delving into the more general scenarios, it's insightful to first examine a particular type of slip DBC: those that are axis-aligned. Understanding this specific case will lay the groundwork for tackling the broader range of slip DBCs.