Hi, I wanna simulate the flow in a 3d square duct (aspect ratio=1) with a cylinder hanging in the duct by a line. the flow is incompressible which is actually issuing from a ventilation fan. In this case, what kind of mesh I should use? Is the side wall boundary layer of the duct important? Many thanks.

Jane

That depends on your Re, Jane...is it laminar or turbulent flow? have you done a dimensionless analysis of the case?

Hi, The side of the duct will certainly have a low influence compare to the front side. However it could interesting to study it. The important part of your mesh has to the boundary layer. Depending on which near wall law you are using you need to decide what Y+ you want, and this will give the size of your boundary layer (or at least the first cell range size). For the rest, make sure your domain is enougth big to let the post-duct instabilities get fully developped.

Bye, Thomas