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Old   June 23, 2013, 20:57
Default Residual vibration
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Hi all,
I have simulated a steady flow around a blunt body. Of couse, the really
flow is unsteady. When I simulated the flow with a coarse mesh, the result of
Cd convergented as well as residual.
However, when I refined the mesh, although the Cd convergented finally but it vibrated between a small range. So was the residual as shown in the pic.
Why? Is it because the fine mesh would catch more unsteady flow details?
And how I can improve the stability?

Thanks.
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File Type: png residual.png (14.2 KB, 11 views)
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Old   June 29, 2013, 20:12
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Chris DeGroot
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Likely the fine mesh is resolving the unsteadiness better. If it is a transient flow and you try solving as a steady flow the residuals will generally not converge and do what is shown in your plot.
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