@steve and Rob
Thank you very much for your responses.
I already calculated the reynolds number at the inlet and outlet, they are small values around 15. It means that the flow is laminar. What I was wondering is regarding the complexity of the fluid volume.
I ran the simulation with laminar flow by refining the mesh and applying inflation layers. The velocity residuals converge but the continuity residual is not converging. The continuity residual can't go below e-2. I also monitor volume flow rate at the outlet. It shows relative stability but it is not perfectly straight.
Do you have any suggestion on how to get the solution converge?