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VIRGINIE November 10, 2005 14:53

Units GAMBIT
 
I would like to work with inches in gambit but I have trouble setting the untis I think I am currently in mm and afterward I put it in fluent and i would also like to mesure un inch. Now the fluent softwar is in m all my units are mixed and I cant get good value because of that. Can you tell me how to change my units in both sofwart.

One more question: how is it possible to obtaine Cl and Cd max in fluent for an airfoild in 2_d

Last question: is it better to use k-epsilone or k-omega to calculate in my aifoild.

Thanks

Virginie Brisebois

Michal November 10, 2005 15:11

Re: Units GAMBIT
 
Hi,

In Gambit you are working with dimensionless units, you have to specify mesh units in Fluent in Grid - Scale.

Bye

Jason November 10, 2005 18:37

Re: Units GAMBIT
 
You can also display what units you want to see in Fluent by going to Define->Units. You still need to scale your grid like Michal said, but this way you can use british units in your boundary conditions, reference values, etc., and also get british units back when looking at the results (like when plotting contours for example).

Fluent doesn't have an automated way of getting CL and CD max. Depending on how you define your boundary conditions, you can change the flow direction, and do this for several angles of attack. Record your values for CL and CD at each AoA in excel or something, and that way you can see the trends vs. AoA. You could do this with a UDF as well (where you vary the boundary conditions and record the CL and CD).

I've seen decent results with k-e realizable and k-w SST (don't use the standard k-e or standard k-w though). The Spallart-Almaras model has the best track record with 2D, steady-state airfoils, as long as you're staying away from stall, and you're paying attention to your y+ values.

Hope this helps, and good luck, Jason


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