Near wall treatments

Pierrm · May 16, 2018, 07:28

Hello there,

I modeled a pump on CFX (and FLUENT) with the SST K-omega model. This model combines the k-epsilon formulation for the free Stream and the k-omega formulation in the boundary layer.

To use k-omega formulation, "the first computational cell must have its centroid in y+ ~1". That means a fine mesh allows the resolution of the boundary layer.
And if the y+ is in the log-layer (30-200), wall functions are used.

But what is happening if we use Automatic wall treatment?
And if the y+ is between 1-30 (in the Buffer layer)?

Thank you all in advance

LuckyTran · May 20, 2018, 03:24

There is a blending function that blends the log-layer formula to linear-layer one. When you are in the buffer layer, the same blended formula is used so nothing changes.

May 16, 2018, 07:28	Near wall treatments	#1
Pierrm New Member Join Date: Mar 2018 Posts: 2 Rep Power: 0	Hello there, I modeled a pump on CFX (and FLUENT) with the SST K-omega model. This model combines the k-epsilon formulation for the free Stream and the k-omega formulation in the boundary layer. To use k-omega formulation, "the first computational cell must have its centroid in y+ ~1". That means a fine mesh allows the resolution of the boundary layer. And if the y+ is in the log-layer (30-200), wall functions are used. But what is happening if we use Automatic wall treatment? And if the y+ is between 1-30 (in the Buffer layer)? Thank you all in advance

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May 20, 2018, 03:24		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,797 Rep Power: 66	There is a blending function that blends the log-layer formula to linear-layer one. When you are in the buffer layer, the same blended formula is used so nothing changes.