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 Michelle August 6, 2004 00:00

Hello, i am constructing my geometry in gambit, but the dimensions of the gasket i am using and my set up are really small, i.e in the order of 0.001mm. if i were to draw such a structure in gambit, it would be too tiny. does it matter , what dimensions i use, or if i scale everything by a factor of 100. what about my inlet flow rate, would i have to scale it too? How would all these affect my results?I would really appreciate any help.

 Michelle August 6, 2004 00:01

 Dan Brzozowski August 6, 2004 00:39

You can scale geometry in Fluent by going to the Grid/Scale... menu. So for example you could just take one gambit unit to be 1 micron. Then after you read the mesh into fluent, scale it by 10^6 in all dimensions.

-Dan

 Oliver August 6, 2004 02:32

That is right Dan but when you scale the grid, only the grid and not the physical value is scaled so if you have 10^-6m3/s as inlet flow rate you have to enter 10^-6. Such value involve convergence difficulties don't you think so?

 Dan Brzozowski August 6, 2004 03:11

I don't think there should be any convergence difficulties since Fluent uses scaled residuals to judge convergence (see User Guide section 24.16.1 "Monitoring Residuals").

If I understand this right, for an inlet flowrate of 10^-6m/s, the default convergence cirterion of 10^-3 would essentially require that the error not exceed 10^-9m/s. Here "error" is defined as some average of residuals from the continuity equation in each cell.

-Dan

 Alex Chirokov August 6, 2004 12:34