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2015-03-14 21:21
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OF_kw.png (172,855 bytes) |
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Which bubbleColumn tutorial are you running? Do you get the same behavior with the laminar, LES and RAS versions? |
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Sorry. It was the 'RAS' tutorial. I have not evaluated the other versions -- will do it and check the results. |
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Results: * bubbleColumn, laminar: same results for the average fields (U*Mean, alpha.airMean), running in 32 and 64 bits. * bubbleColumn, LES: idem; instantaneous k fields were also similar each other, reaching maximum values (near the same spots) of 0.139 m²/s² -- between those obtained using RAS-64bits (0.001 m²/s²) and RAS-32bits (0.298 m²/s²). What originally caught my attention, in the RAS tutorial, was the different U.waterMean obtained running it in 32 bits. Comparing all runs, it was the only one that was not symetrical. Each simulation was calculated in a single process. And, for the record: the 32 bits system was, in fact, used in a machine with a 64 bits processor. |
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This is what I expected, the issue is with the mixtureKEpsilon model. Try with the continuousGasKEpsilon for air and LaheyKEpsilon for the water, I expect the results will be the same 32bit and 64bit. |
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Indeed, the results obtained using continuousGasKEpsilon and LaheyKEpsilon were the same using version 2.3.1, 32bits and 64bits. Thus, until the mixture model is corrected, the recomended way to get consistent results (in RAS approach, using v2.3.1) would be to model the turbulence for each phase? |
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I am working on the mixtureKEpsilon model anyway due to problems with the behavior of inlet-outlet BCs which may also relate to the issues you see. Should be fixed in a few days. |
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OK, thank you very much! Best regards, Leonardo Rosa |
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I have pushed a change to the mixtureKEpsilon model in OpenFOAM-dev and updated the bubbleColumn tutorial. The change supports km and epsilonm to be read from the initial time directory allowing correct specification of inletOutlet BCs etc. Note that the epsilon wall-function is not specified in the epsilonm file but instead applied to epsilonm from the phase epsilons. I know this is a complex specification but necessary given the way in which the model operates on both the phase and particular definition of mixture turbulence properties. It is likely that this change to the inletOutlet condition will resolve the problem you see running 32bit; could you test and report back? |
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Sure, I'll check and report any issue. I just need some time to setup a 32bits dev environment. Meanwhile, some headers were strangely missing to compile my (updated) local repository. Luckily they can be "found" using: $ ln -s $FOAM_SRC/finiteVolume/cfdTools/general/include/gh.H $FOAM_SRC/finiteVolume/lnInclude $ ln -s $FOAM_SRC/finiteVolume/cfdTools/general/include/readhRef.H $FOAM_SRC/finiteVolume/lnInclude |
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You will need to update the lnInclude directories. Simply clean them out and they will automatically be rebuilt: wcleanLnIncludeAll Note that the lnInclude directories are created by wmake, they are not present in the git repositories or source-packs. |
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I have just pushed an update to the mixtureKEpsilon model which should significantly improve numerical stability and may also help with consistency between 32bit and 64bit operation. |
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I will close this report for now as I believe the problems are resolved in OpenFOAM-dev. If you still experience the problem please reopen this report. |
- Anonymous
