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November 17, 2015, 20:29 |
Wall functions and openfoam
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#1 |
New Member
Matej Muller
Join Date: Oct 2011
Location: Slovenia
Posts: 25
Rep Power: 14 |
Hi!
I know, there are already meany threads on this topic on the forum, but I'm still a bit confused when it comes to wall functions in openfoam. Can anyone explain what is the difference between calculated and nutkWallFunction for the nut BC . I've noticed that if I use k --> kqrWallFunction epsilon --> epsilonWallFunction nut --> calculated instead of k --> kqrWallFunction epsilon --> epsilonWallFunction nut --> nutkWallFunction I get better results according to my measured data. If the wall function is already included in k and epsilon, why do we have to use it also in the nut file... Or is this approach with the calculated BC totally wrong (the y+ values are greater than 30). Also, if I use the k-omegaSST model, do I have to use the nutUSpaldingWallFunction for the nut BC if my y+ values are somewhere smaller than 5? I know the omegaWallFunction works well for lowRe and HighRe flows, but I'm not sure if that is true for the nutkWallFunction? But even if I use omegaWallFunction and nutUSpaldnigWallFunction, I still have to use the kqrWallFunction, which I know is not good for lowRe flows. So what would be the right approach in using the k-omegaSST model? Any comments would be appreciated. Regards, matej |
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November 19, 2015, 11:08 |
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#2 | |
Member
Eric Robertson
Join Date: Jul 2012
Posts: 95
Rep Power: 14 |
Quote:
For SST, you should be able to use a direct condition of nut ~ 0 on the wall if your y+ is that small. Why is kqrWallFunction not good for low-Re formulations? |
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