Problems with wall shear stress.
 

Hi, I am doing some simulation on non-Newtonian fluid flow through a stenosed pipe with a bypass pipe. I am very interested in the wall shear stress after the bypass. I add boundary layers at the walls, the inlet and the outlet, as well as the intersections. However, when I compute the wall shear stress, it doesn't seem to converge when I refine the mesh, especially the minimum value there.

I generate the mesh under GAMBIT. Can you give me any suggestions? How accurate does FLUENT give us in the sense of wall shear stress?

Another question is that when I want to get the minimum of wall shear stress, Fluent gives me two options: facet minimum and vertex minimum. What is the difference between them? How does FLUENT compute them? Which one is more reliable?

How to get a converged solution for wall shear stress?
 

Hi, I might not demonstrate my problem clear.

I have boundary layers near the walls and at the intersections. However, when I decrease the size of the first raw in the boundary layers while keep the major part of the mesh to be the same, I don't get a converged solution for the wall shear stress. I am interested in the minimum of the wall shear stress near the intersections. However,the values keeps changing when I refine the mesh. My case is laminar flow. This confuses me a lot.

Does anyone have any suggestion?:confused: