missing p.relax() in pisoFOAM
One can find at the end of simpleFOAM the code line
/ / Explicitly relax pressure for momentum corrector p.relax (); but this line is missing in pisoFoam.C. Why? best regards, V. G. |
piso Foam is a transient solution so relaxation can not be true for a transient solution;) look CFD book you can find more about difference between piso and simple algorithm
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You can also use relaxation with transient solutions, see eg. PIMPLE or transient SIMPLE. However, the whole point about the PISO algorithm is to eliminate the need for underrelaxation. I do agree with you VG. should have a look into a CFD book on this though.
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and whats the difference between p.relax() with PEqn.relax()? BTW, in Verssteeg'book page196, it said: Quote:
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It doesn't really matter that much if you relax UEqn. In fact, you can throw out the solution UEqn completely by deactivating the momentum predictor.
As for your question about the two types of relaxation, this has been answered multiple times in the past, e.g. here. Quote:
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In SIMPLE, cuz there is an omission of velocity correction of neighbor cells, using this u^' to correct velocity is moderate. But for pressure, using this u^' to correct pressure is exaggerated. Cause we need to do explicit relaxation in pressure field to make pressure correction to be moderate. |
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