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-   -   Is FASTRAN sensitive to the grid? (http://www.cfd-online.com/Forums/main/94357-fastran-sensitive-grid.html)

june_zhazha November 13, 2011 08:58

Is FASTRAN sensitive to the grid?
 
I use FASTRAN to calculate the AGARD-B model in the wind tunnel, so i don't change the inlet conditions . I ratate the model to get the angle of attack ,such as 2,4,6,but when the angle of attack was 6, the process running by first order form converged ,but the process running by second order form was suddenly divergent.

Is the FASTRAN so sensitive to the grid?

cfdnewbie November 13, 2011 09:50

I havent used fastran, but what you are describing sounds like you changed the discretization from first to second, right? then it's no wonder higher AOA will give you more vortices, and thus unsteadiness...

june_zhazha November 16, 2011 10:28

Quote:

Originally Posted by cfdnewbie (Post 331868)
I havent used fastran, but what you are describing sounds like you changed the discretization from first to second, right? then it's no wonder higher AOA will give you more vortices, and thus unsteadiness...

Then how can i improve the calculation?

cfdnewbie November 16, 2011 14:11

If the problem itself is unsteady due to high AOA, then that's the real physics, and your first order is way too dissipative!
Refine the grid, use higher order (4,6,8,....) schemes....


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