I am experimenting with a very simple two way FSI. A solid square is moved through some air. I place a prescribed displacement on the bottom of the square. What seems to happen is an actual gap in the mesh appears at the bottom of the mesh at the prescribed displacement ( dont mean a stretched mesh)
You can see the gap as a white section in the default view and it is obvious in the mesh plot (both images attached).
Is a prescribed displacement illegal in a two way FSI on the boundary of the solid/liquid interface ? If so, how does one force a movement of one section of a solid ?