Hello Deal.II Users,
I am working on setting a constraint: (V - v_s ) \cdot n = \phi_f (v_f - v_s) \cdot n on three vector variables at the interface with affine constraint class in Deal.II's library.
(Where, V, v_s, and v_f are velocity vectors on two different domains, and they are coupled with each other at the interface; n is the normal vector; \phi_f is the volume fraction.)
I decided to constrain either V_x= -(...) / n_x or V_y= -(...) / n_y depending on the absolute values of n_x or n_y (n_x and n_y are the components at x, y directions of the normal vector n).
Now, I have a problem with getting the normal vectors at nodes when playing with affine constraint within the fe_nothing and hp:finite element framework. The relevant function/class I have found in Deal.II's library all return the normal vector at quadrature points, not at nodes.
Have you ever encountered a problem like this? Could you kindly share me your idea of handling this problem? Thousand of thanks.
Best,
Lei Li