The Roller node adds a roller (sliding wall) constraint as the boundary condition; that is, the porous matrix displacement is zero in the direction perpendicular (normal) to the boundary, but the porous matrix is free to move in the tangential direction. The condition can be added from the
Porous Matrix Conditions submenu and it can be combined with any of the conditions found in the
Fluid Conditions submenu.
) and select Advanced Physics Options in the Show More Options dialog box.