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April 30, 2001, 07:18 |
drag predicitions
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#1 |
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Hi everybody ...
As most of you are aware, for creeping (slow) flow of Newtonian fluid moving over a sphere the ratio of pressure coefficient to viscous coefficient should be ~ 0.5. Unfortunately, when I use Fluent 5.3, it is not the case. The total coefficient is right, namely, for Re = 0.01, the total drag coefficient should be ~ 2400. I got it 2400.8. However the ratio of pressure coefficient to viscous coefficient is 640.66629/1760.1434 = 0.36. Could anyone think of possible reason. |
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May 2, 2001, 13:33 |
Re: drag predicitions
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#2 |
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I would do a mesh adaption based on pressure gradient. And then do a second mesh adaption based on velocity gradient. After those adaptions, run it again and see if you observe any changes.
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May 7, 2001, 22:12 |
Re: drag predicitions
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#3 |
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I have the same experience. In most cases, mesh adaption is the key point,because the accuracy of viscous coefficient rely on the mesh quality. I would inspect into the velocity profile and see if the velocity gradient in boundary layer is smooth. That's important, I think.
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