Hey @hmattoo
interesting project you have there
in main time if you expecting a flow separation you have to do more on your mesh when all solids pass through fluids or stationary objects subjected to moving fluid they acquire a boundary layer of a fluid around them when the viscous force occurs in the layer of fluid close to the solid surface, bcause Flow separation occurs when the boundary layer travels far enough against an adverse pressure gradient that the speed of the boundary layer relative to the object falls almost to zero, to capture this effect we add inflate boundary layer in our mesh but yours don’t have that. if you take a CFD master class course in the simscale academy you can find a nice example for meshing such problem in session one
exercise
and I am wondering why you model the rood as moving wall?