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-   -   modelling flow in microchannel (http://www.cfd-online.com/Forums/fluent/27936-modelling-flow-microchannel.html)

Wang October 9, 2000 11:42

modelling flow in microchannel
 
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?


Whitaker October 9, 2000 14:42

Re: modelling flow in microchannel
 
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

Rüdiger Schwarze October 10, 2000 04:12

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

Rüdiger Schwarze October 10, 2000 04:19

Re: modelling flow in microchannel
 
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.

Wang October 10, 2000 06:13

Re: modelling flow in microchannel
 
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.

Rüdiger Schwarze October 10, 2000 09:13

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

Wang October 10, 2000 09:28

Re: modelling flow in microchannel
 
good idea. I try it.


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