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Is FASTRAN sensitive to the grid?

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Old   November 13, 2011, 08:58
Default Is FASTRAN sensitive to the grid?
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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?
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Old   November 13, 2011, 09:50
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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...
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Old   November 16, 2011, 10:28
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Quote:
Originally Posted by cfdnewbie View Post
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?
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Old   November 16, 2011, 14:11
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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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