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September 1, 2006, 14:59 |
I've tried to run some 3D simu
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Steve Berg
Join Date: Mar 2009
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I've tried to run some 3D simulations with a Reynolds stress model lately, but they will not converge. I've played around with the settings and variables but the simulations remains unstable. However, with the k-epsilon model the simulations converges nicely. Have anyone else had succees with the RSM, or am I doing something utterly wrong?
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September 1, 2006, 15:19 |
It should work without problem
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Hrvoje Jasak
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It should work without problems. If you are running something relatively small and simple I wouldn't mind having a look, just to make sure RSTM is still fine.
Hrv
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Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk |
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September 2, 2006, 05:21 |
It's a small case where two sq
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Steve Berg
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It's a small case where two square ducts, each of them with dimensions 0.1*0.1*1 (m), are joined together in a 90 degree bend. Air is flowing through at a Reynolds number of 100,000. The turbulence intensity, and the turbulent length scales compared to the outer dimensions, are both assumed to be 10 %.
The kEpsilon and RNGkEpsilon works well on this geometry, but I cannot obtain a solution with the LRR or LaunderGibsonRSTM models. |
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September 2, 2006, 05:40 |
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Steve Berg
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September 2, 2006, 05:48 |
Steve,
I don't think you ma
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Hrvoje Jasak
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Steve,
I don't think you managed to attach the file. Hrv
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Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk |
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September 2, 2006, 05:49 |
Hi,
Im a beginner att openF
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#6 |
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Hi,
Im a beginner att openFOAM but I have tried the turbmodels you mension and I have had a similar problem which i got thru by having a epsilon value 3 times as big as when I used the kepsilon models. /erik |
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September 2, 2006, 08:15 |
I'll try again:-)
Here is a
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#7 |
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Steve Berg
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September 2, 2006, 15:02 |
I don't see a problem: it conv
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#8 |
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Hrvoje Jasak
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I don't see a problem: it converges monotonically. This is what I did:
- run 100 iterations with k-epsilon - calculated Reynolds stress using R - restarted with Launder-Reece-Rodi RSTM. Converges smoothly with no trouble. I can either give in normal stress only at the inlet of the full equilibrium R from the k-epsilon model. A few comments: - your numerics is rubbish: you should try using second order - if you try to start up LRR from the beginning it blows up because of epsilon. You should really start k-epsilon and restart; otherwise you will have fun trying to set up under-relaxation coefficients - at the end of the residual graph you start hitting solver convergence tolerances: hence the plateau - I can make this even better using my fixedMeanValue outlet b.c.: makes it prettier close to the outlet Hrv
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Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk |
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September 3, 2006, 12:00 |
Hi Hrvoje
I didn't now abou
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#9 |
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Steve Berg
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Hi Hrvoje
I didn't now about the "R" function. When I followed you steps the solution converged without problem. Thank you Steve |
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August 15, 2010, 07:14 |
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#10 |
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Daniele
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Hi
I try to use LRR for my simulation. I'm simulating an atmospheric boundary layer, but my result with it are completely different from the same case with k-eps model. Post my case. Thanks |
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February 25, 2014, 19:39 |
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#11 | |
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CHARLES
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Quote:
Could you please provide an fvSchemes and fvSolution that aren't "rubbish"? I'm not very well-versed in numerical methods (yet!) and would like to get a better idea of what 'good' settings for LRR are. Thanks! |
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