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July 6, 2009, 13:20 |
Problem using PISO
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#1 |
Senior Member
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Hi Foamers,
I am having some problems using PISO to simulate the flow of complex fluids, in particular polymers, where some extra stresses have to be considered. I can already simulate the flow in a simple system, infinite parallel, but when I compare the analytical solution with the predictions of OpenFoam, I manage to obtain the correct velocity profile but the predicted pressure gradient is smaller than expected. On possible problem is the analytical solution is wrong, but I doube check it and it is correct. I am thinking on the the possibility of doing more PISO steps, to improve the calculation of the pressure field, or changing the PISO algorithm implemented in icoFoam, that I am using. Has anybody any ideas of what is going on? Any help will be much appreciated. Regards, Titio |
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July 7, 2009, 02:26 |
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#2 |
Senior Member
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,912
Rep Power: 36 |
Hi Antonio,
first, an elementary question: is the pressure gradient wrong or is the value of pressure simply different? I ask because if you use an incompressible solver in OF, the actual value of the pressure you find depends on the reference value. However in such a case the gradient should be OK. About your specific case, without knowing more on the model you use to describe the non-Newtonian stress tensor, and how you implemented it, it is impossible to reply. Best, A.
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Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541) OpenQBMM - An open-source implementation of quadrature-based moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using. |
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July 7, 2009, 05:48 |
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#3 | |
Senior Member
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Quote:
The pressure value is simply different, by at must 10%, I tried to change the mesh and the problem remains. I am testing the possibility of iterating several times in a PISO step, this time including the momentum predictor. Do you have more ideas? Regards, Titio |
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