Hi @yagiwal: I took a look at your project (CFD Pump4) just now. The geometry you imported into that project is wrong (Simscale_project_1). There are two solids, which is OK, but the MRF zone (one solid) should be just a cylinder, without void. Currently your MRF zone does contain all faces of impeller.
The example project I suggested to study, explains that quite well.
Now, the “Pump” itself should become just an internal air (or water) volume. That volume will contain all faces (boundaries of that volume) and on those volume faces, internal or external, you can calculate Forces and Moments.
In that respect my statement “calculating forces on void do not work” is possibly misleading. You are using volume faces, when they are defined, In your case all internal pump elements will have those faces you will define as ‘non-slip’.
So please first fix your geometry, remesh it and check that MRF zone is correct (not crippled MRF zone mesh like you have now).
Cheers,
Retsam