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unphysical pressure increase at outlet

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Old   January 21, 2010, 07:13
Default unphysical pressure increase at outlet
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Martin Becker
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I am simulating a waterturbine stator flow channel (with cyclicGgi) with two fixed blade rows (1 stayvane & 2 guidevanes).
I have stable and converging results that are not too much away from reality, except in one point:
In the outlet region, I get an unphysical increase in static pressure and decrease in velocity.

My boundary conditions are:
- inlet velocity profile, defining Q and the inlet flow angle
- walls (hub, shroud, guidevanes, stayvane)
- cyclic periodic symmetry (cyclicGgi)
- outlet pressure: fixedMeanValue = 0
- average y+ is ~40

I am using the k-omega-SST turbulence model, as I found the exaggeration of k-epsilon in the stagnation point to be too extreme.
I already tried to use a finer mesh in the outlet region, but that doesn't help.
The mesh quality is fine (worst angle 30).
I also tried to use fixedValue = 0 at outlet for pressure, same result.

I simulated the case on the same mesh with same bcs with CFX and attached some pictures that show the solution in a middle plane (static pressure and velocity magnitude for CFX and OpenFoam). I also attached my 0-files + fvSolution, fvSchemes and boudary files.

Thanks for your help,
Attached Images
File Type: jpg p_CFX.jpg (85.3 KB, 14 views)
File Type: jpg p_OpenFoam.jpg (82.4 KB, 11 views)
File Type: jpg Uabs_CFX.jpg (83.3 KB, 11 views)
File Type: jpg Uabs_OpenFoam.jpg (88.0 KB, 9 views)
Attached Files
File Type: gz 0_boundary_fvSchemes_fvSolution.tar.gz (2.6 KB, 4 views)
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