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Old   October 11, 2013, 14:33
Default simpelFoam, SRFSimpelFoam and MRFSimpleFoam
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Pengchuan Wang
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Hello everyone,

I'm new to OpenFOAM and I ran some simple cases using simpleFoam. Now I want to move to rotating reference frame. So I ran three cases separately in simpleFoam, SRFSimpleFoam and MRFSimpleFoam. However, the results from simpleFoam and SRFSimpleFoam are exactly the same, but they are different from the result from MRFSimpleFoam. I don't know why. I think they three should be exactly the same. And I attached these cases in the attachment. Maybe I setup the model in a wrong way. Please give me a hand. Thank you so much.
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File Type: zip Diff.zip (35.3 KB, 10 views)
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Old   October 12, 2013, 08:24
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Nima Sam
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Quote:
I don't know why. I think they three should be exactly the same.
why it should be the same? as you said MRF or SRF are rotating frame, so their result should be different with simpleFoam
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Old   October 12, 2013, 10:38
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Hi Nima,

Thank you for your reply. Yes, they are rotating reference frame, but the model is the same, they just use different method, so the absolute velocity distribution and pressure distribution should be the same. And actually the results from simpleFoam and SRFsimpleFoam are exactly the same. They are the same with analytically solution. But the result from MRFsimpleFoam is different.
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Old   October 12, 2013, 11:13
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Nima Sam
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Are you using rotating Frame or not?
if yes, then it should be different between fixed frame of simpleFoam and rotating frame of MRFSimpleFoam and SRFSimpleFoam.
also you need to provide some contour and more information about your set-up then other users can help you
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Old   October 12, 2013, 11:50
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Hi Nima,

Yes, you are right, I should provide more information. I attached three pressure plots. In the plots, there are only two patches, one is inlet and the other is rotating wall. I set the pressure at inlet is zero. The pressure plots from simpleFoam and SRFSimpleFoam are nearly the same, but the plot from MRFSimpleFoam is different. There is a pressure discrepancy at the junction of the rotating wall and the inlet. But this discrepancy does not exist in simpleFoam and SRFSimpleFoam. That's my question. And I still don't understand why the results should be different. Though they use different methods, they still solve the same equation, and the results should be the same.
Attached Images
File Type: png MRF.PNG (65.6 KB, 25 views)
File Type: jpg SRF.jpg (29.6 KB, 23 views)
File Type: jpg simple.jpg (27.7 KB, 24 views)
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