y+ calculation (for no wall function walls) (and its BC)
Dear experts,
When i use wall function i can see y+ by yPlusRAS and yPlusLES command. it calculate min, max and mean of y+ and write it on terminal. But when y+<5 i don't need wall function and i set wall as zerograDient. but by above commands no y+ would be written on terminal: Code:
Time = 0.47 Code:
lowerWall it may because it is zeroGradient nut, K, epsilon, R so what BC should be used when no need to wall function. U is set value 0 not zeroGradien. Regards |
Use wallGradU and formula 7.24 from pope:
tau_wall = rho*nu*(dU/dy)_wall However, this will only work if first y+ is really small, say around 1. You can use this is an wall-resolved LES or DNS. |
sorry, double post
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sorry, double post
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But this formula won't give me y+. i want see y+ value by yPlusRAS or yPlusLES |
yPlusLES works fine for me.
Why does it not work for you? |
yPlusRAS works when the patch setting be nutWallFunction.
When it be set as zeroGradient above output is seen. |
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y+=(y/nu)*sqrt(tau_wall/rho) Youll'have simply to know the height y of your first near wall node and then you can calculate y+ wherever you want, by sampling wallGradU or directly wallShearStress (both of these utilities work also without wall functions as bcs) Regards V. |
My problem is yPlusRAS dosen't work for me.
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V. |
Thanks Vesselin
It is strange because yPlusLES works for a LES case without wall function but yPlusRAS doesn't work for a LRR case without wall function. |
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