[MultiPhy]

I want to create a very simple model: A fluid channel with Stokes flow, with a sphere (2D is fine too) in it that gets pushed along by the fluid.

This is easy to do if you use the Fluid-Structure Interaction (FSI) module to connect the solid and liquid physics. But, the FSI module can be limiting (e.g., it does not allow specifying the sphere as a rigid domain -- it must be elastic) so I'd like to set the model up without it.

To do this, I am using Creeping Flow, Structural Mechanics, and Moving Mesh. From Structural Mechanics I added Rigid Domain to the sphere and then tried to couple the forces of the fluid to the sphere with various combinations of things in Moving Mesh (e.g., Prescribed Mesh Displacements, Prescribed Deformations) and Structural Mechanics (e.g., Prescribed Displacement, Applied Force, Applied Moment).

This seems like it should be simple, but no matter what I do my sphere won't move at all . Any input would be greatly appreciated!