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April 3, 2020, 05:56 |
turbulence in compressible cases
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#1 |
New Member
Edmund Teller
Join Date: Feb 2020
Posts: 12
Rep Power: 6 |
Hi all,
I've been having some trouble with understanding the turbulence models in the compressible case, I have a cell that is essentially a cuboid with a central pillar cut out of its central (long) axis, so a slice through it would look like: Code:
side view: ____ ____ | | | | | | | | | | | | | | | | |___| |___| top view: __________ | ____ | | | | | | |__| | |________| So, the solver I've been running is essentially mhdFoam combined with rhoPisofoam, as in the paper by Carlos Xisto (https://doi.org/10.1016/j.jcp.2014.07.009), so there are magnetic fields applied to generate the velocities. The issue I've been having is that the velocities always diverge: all of the turbulence properties I set in the /0/ folder (k,nut,omega for RAN omegaSST and k,nut for LES) seem to be calculated, so their values immediately starts to decrease from the internalField values I set on the first iteration and turbulence seems to have less of an effect. For the walls I have a kqRWallFunction, nutkWallFunction, omegaWallFunction set for k, nut, and omega respectively, and all have zeroGradient set for the outer patches, with internal fields set to 1e5, 9e-3, 1.11e7 values for the internalField of k,nut,omega respectively. My question is how do I increase the effect of the turbulence on the velocities to damp these instabilities? I don't really understand where to set constants to increase the effect of turbulence since every variable (k,nut,omega) seems to be calculated, should I be setting the outer patches to fixedValue? Should I just increase the viscosity mu in thermophysicalProperties? Thank you. Last edited by edmund32; April 3, 2020 at 06:08. Reason: ASCII art got messed up |
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April 8, 2020, 04:44 |
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#2 |
New Member
Edmund Teller
Join Date: Feb 2020
Posts: 12
Rep Power: 6 |
bumping for response
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Tags |
compressible komegasst, compressible les, mhdfoam |
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