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Discretization Error vs Residual Error?

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Old   March 20, 2012, 23:09
Default Discretization Error vs Residual Error?
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Daniel
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Hello all,

I just ran a sensitivity study on my case to see if I could improve my accuracy by using SFCD (2nd order scheme for convection terms) vs linearUpwind (1st order accurate). All else being equal, the SFCD case had a p-residual of 5e-1 and the linearUpwind case had a p-residual of 10e-3. I expected better accuracy from the 2nd order accurate case, but the residuals appear to show that was not the case. I am running simpleFoam on a 2D airfoil. Could anyone please suggest why the residual is higher for the 2nd order scheme?

More strange behaviour: the SFCD took LESS time to execute the case, and resulted in values of Cd and Cm that were farther from the experimental data than the upwind scheme. I expected different. Can anyone explain this?

Thanks,

Dan
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Old   March 21, 2012, 03:49
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Anton Kidess
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I always thought linearUpwind is 2nd order upwind. Is plain "upwind" what you were intending to compare to?
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Old   March 26, 2012, 20:05
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Hello Anton,

Thanks for finding my error, I appreciate it.

Regards,
Dan
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