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y+ values calculation in OpenFoam

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Old   March 7, 2013, 12:34
Exclamation y+ values calculation in OpenFoam
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AndreiCFD
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Is it anyone familiar with the calculation of the y+ value as well as the turbulent KE and turbulent omega?

I am have an airfoil and I am using Komega SST with simpleFoam with wall functions and when I look at my residuals my pressure doesn't drop and I am ending up with high residuals.

I am interested to drop my residuals below 10^(-4).......

Any ideas

Many thanks

Andrei
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Old   March 8, 2013, 04:13
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Sasan Ghomi
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If your problem is caculation of y+ , So you can use :
yPlusRAS -----> incompressible flow
yPlusRAS -compressible ---------> compressible flow

Sasan.
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Old   March 8, 2013, 04:23
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Ok then.

I run yPlusRans but i get a min value a max value and an average value... what does mean?
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Old   March 8, 2013, 06:27
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Hey there,

i guess you are referring to yPlusRAS when you wrote yPlusRans?

However to answer your question:

y+ value is a dimensionless height of the first cell on a surface.
But when this cell hight is varying over the surface you get different values.

Since providing the cell heights of all cells is quite a lot information
as a rough indication only the smallest the highest and the average of
all cell heights are given.

Usually the max value is the most crucial one since you can see with this
one whether the values exceed the maximum allowable for using
wall functions.

I hope this helps
regards
Colin
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Old   March 8, 2013, 06:39
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AndreiCFD
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so for a High Re I should have a yplus around 30 when using wall functions
therefore I should keep an eye just on the max value of the yplus when running yPlusRas....
Collin correct me plz if I am wrong.
Thanks
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