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Meaning of PISO Corrections

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Old   February 26, 2017, 15:02
Default Meaning of PISO Corrections
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Hello. I am doing a transient simulation and want to use PISO as the pressure velocity coupling scheme. After reading the theory guide, I understand that the skewness correction is for highly skewed meshes and neighbor correction is to get a more accurate solution. But I couldn't find as to what the values (default 1) of both these fields mean? My mesh has almost little to none skewness. So do I make the skewness correction value as 0? What about the neighbor correction value?
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Old   February 26, 2017, 19:37
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Leave them as the defaults.

I actually can't discern the details either and it's not well documented. The problem is that there are too many things going on and these options are implemented in the style of under-relaxation whereas they are discrete steps in the PISO algorithm. I.e. you do an extra neighbor correction step and an extra skewness correction step so the values should be integers like 0,1,2,3, etc... But that's not the way the menu is set up. It probably has something to do with the AMG solver.

My guess is the corrections are always calculated and you apply an under-relaxation factor. If that is so, then setting neighborCorrection to 0 would turn PISO into SIMPLE. You could probably set the skewness correction to 0, but if it is always calculated then you would not get any speedup, and it would slow down your convergence. So unless someone knows better, I would leave them as they are because they don't hurt.
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