In a previous post about hybrid meshes, non-conformal mesh interfaces were discussed as they relate to the connection of the faces of different mesh cell types—and the recommendation was that such interfaces be avoided, if possible, due to potential problems with the interpolation of fluxes between adjacent cells. However, when modeling a system with a moving part, such as an impeller, rotor, or screw, a non-conformal mesh interface is unavoidable, since a sliding mesh is required for a time-accurate solution. Both the moving and stationary mesh zones are bounded by a face with the same shape for both zones, but the meshes are unconnected so that they can slide relative to one another.
For these sliding meshes, the cell sizes of each non-conformal interface should ideally be relatively similar and, especially for rotational systems, the mesh should be fine enough to capture the curvature of the interface, since the adjacent cells could otherwise interfere with one another as they rotate relative to one another. And finally, for an accurate solution, the time step used in the simulation should be small enough so that the relative motion is not much more than the cell face size.