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High Pressure and Turbulence

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Old   July 14, 2020, 15:27
Default High Pressure and Turbulence
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Andy Robertson
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Folks,
I have a high pressure device flowing air through a series of baffles.
Working pressure around 2000psi
I am using ideal gas law and Standard K-Epsilon.
Max Mach number around 0.2
I am running into the TVR limiter almost everywhere.
Mass and pressure seem well converged.
But the turbulent viscosity field seems unrealistic.
I would expect high values in the baffles themselves, but not in some of the low velocity regions.

Is there a pressure dependency to the turbulent viscosity I am not understanding. IE should I just set the limiter an order (or two) of magnitude higher.
Andy
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Old   July 15, 2020, 01:26
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Might be coarse mesh.
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Old   July 15, 2020, 12:07
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Andy Robertson
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It may be a mesh density issue.
However, I am wondering if this is related to density through the normal stress.
As I recall (and I may be a bit out of date here) Star's (and other's) implementation of K-E results in an unphysical turbulent viscosity in regions of high normal stress. And as the K term is per unit mass, and I have a high density (at least for a gas) so perhaps that overshoot due to normal stress is magnified.
I am going to try increasing the mesh density a bit (have to keep the run time finite ;-) and perhaps shift to the realizable KE.

Not a high swirl device but may even try RSM

Any other thoughts out there?
AndyR
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