Hi, I am modelling laminar flow in microchannel. I have two problems:

1. When changed flow materials I got same results. All of them are under same boundaries and same geometry. What is wrong?

2. Comparison with exact results there is a big error.

Modelling laminar should be a simple case. What result in these problems?

Hi, Wang,

I do not quite understand your question. In your case, I believe only the Reynolds number matters. If you change your flow material but the Reynolds number (Re = density*velocity at the inlet*(2*the height of the channel)/viscosity) is kept the same, the results shouldn't make any difference from your previous case.

Whitaker

If you change the flow material but not the geometry, the viscosity and therefore the Reynolds number will be different, too.

Are you sure that the mesh will resolve the boundary layer of the laminar flow field? Check the sections 5.2.2 and 6.13.3 of the fluent manual to get information about the meshing of laminar flows.

I created the mesh in GAMBIT. I want to further fine the mesh, but the resolution of GAMBIT is limited. Furthermore, when the microchannel is small, the cure of geometry will not be smooth in GAMBIT.

Perhaps You have to build and mesh Your model in meters. You can change the size of the grid using the "scale grid" option.

good idea. I try it.