nnThank you for your response. I am attaching the general picture of the mesh and also the area of flow separation. My colleague used the same mesh for Openfoam simulation and got good results.nThe inflation layer thickness is 0.00001 m and there are 11 layers of the same thickness. Moving away from these 11 layers, the shape isn't a perfect rectangle/square but the thickness is close to the inflation layer thickness for many more layers.nI tried using PISO but the solution always diverges (Either I get Floating Point Error or Convergence issues after running for a while). SIMPLEC is much better in that aspect but the Cd value is still low. I haven't tried PBCS yet so I do not have much idea about it.n