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Inviscid Flow Convergance issues

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Old   July 20, 2010, 22:49
Default Inviscid Flow Convergance issues
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James Merkel
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I am currently doing a inviscid flow simulation over a body and appear to be having a convergance issue. My Residuals were for momentum and continuity were settling around .1 and .01 and not dropping any lower. however when i monitor lift and lift coefficient, they appear to be converging perfectly within .5% Is this acceptable? i have tried dropping the relaxation values for the segregated flow model but still no change..

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Old   November 19, 2010, 14:18
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Depends what software you are using. With most CFD software (STAR-CCM+) you can set up monitors for different convergence factors and monitor those as well. For example, if you are interested in the concentration of a species in a sensitive area, you could set up a volumetric average monitor for that specific species and watch the actual number converge. Residuals are necessary, but can be misleading. You might have a converged solution in front of you and not know it by only looking at the residuals. Another example would be if you were modeling a small server room and were interested in the temperatures in that space. Instead of watching the residual for energy, you could set up a monitor to watch the volumetric average temperature throughout the room. You will notice this monitor converge towards a single number whereas your residual might not show what is considered convergence. Hope this helps..

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