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-   -   which model is suitable? (http://www.cfd-online.com/Forums/cfx/23676-model-suitable.html)

eric February 23, 2007 02:31

which model is suitable?
 
Dear Friends,

In CFX, which model is better for calculate high speed(M =1), compressible air? K-e model??

Thank you in advance.

Eric

sam February 23, 2007 08:05

Re: which model is suitable?
 
SST

Eric February 23, 2007 08:28

Re: which model is suitable?
 
Thank you.

And which is better, upwind or high resolution?

Thank you in advance


Houman February 23, 2007 10:09

Re: which model is suitable?
 
Hi Eric,

about upwind: it is more robust, needs less computaional time and is less accurate...

on the other hand, about high resolution: it is less robust, needs more computaional time, is more accurate and also need finer grid size...

so, you have to decide, which on fits to your problem more!!

Best regards, houman


Eric February 23, 2007 10:11

Re: which model is suitable?
 
Many Thanks


Phil February 23, 2007 10:20

Re: which model is suitable?
 
Just the opposite: high res, being more accurate (mostly second order rather than first order), actually requires a less fine mesh than upwind in order to achieve a mesh-independent solution.

High res is also (generally) quite robust - it is the default!

In general, avoid upwind.

Johnny February 24, 2007 07:01

Re: which model is suitable?
 
I agree with Phil. Only use upwind to get a solution started. Always switch to high res for final solution.

sam February 24, 2007 10:24

Re: which model is suitable?
 
Johnny is right

HekLer February 27, 2007 18:48

Re: which model is suitable?
 
Upwind = You are more likely to get a "conservation satisfying" answer but it is wrong.



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