Apologies for the delayed response. I am still facing the same problem with buoyancy forces. I tried all possibilities with having operating pressure and density as zero and non-zero (101325 pa, 1259.9 kg/m3). I am still getting my drag forces very close to the weight of the body. Which means the drag forces are not considering the buoyancy effects. I also observed that when i specify the operating pressure for initial time step (t=0) , pressure value was applied to entire fluid domain. But in real Pressure increases with depth. Is it because i dont have any inlets/outlets? I checked the pressure contours and i see the gradient for t>0. Could you please suggest a way forward?