To discuss the flow behavior predicted by CFD for expension pipe flow, such as, vortex shedding and pressure indrease at outlet, etc. Please aware that software is not goal to study. The flow behavior in term of all flow physics is what we need to focus on.

The flow boundary conditons, such as, velocity inlet and pressure outlet and numerical scheme for example first order and high resolution to solve problem should be indicated.

all sensible discussion of flow behavior for case such as flow in an expansion pipe.