Wall Y+ value in the buffer region

Bisht · February 24, 2016, 18:50

Hi, I am bit confused about the wall Y+ value requirement for Realizable k-epsilon model. In order to resolve the viscous sublayer, it should be below 1 and for application of wall function it should be above 30.
But what will be the accuracy of the result for y+ value in range of 5-25,i.e buffer region.
From the Star-CCM+ user guide, I got to know about the Two layer all y+ wall treatment which basically switched between high Y+ and low Y+ wall treatment according to Y+ value. But what will happen when y+ value is between 5-25? Can Realizable k-epsilon model resolve it efficiently?

Blanco · February 26, 2016, 07:35

Short answer :no ;-) none of the rans turbulence models is appropriate in the buffer region, even if sometimes the high re approach could give good results also when y+ is as low as 11-15, but this is very case dependent.

February 24, 2016, 18:50	Wall Y+ value in the buffer region	#1
Bisht Member Kamal Bisht Join Date: Jun 2015 Location: Germany Posts: 57 Rep Power: 10	Hi, I am bit confused about the wall Y+ value requirement for Realizable k-epsilon model. In order to resolve the viscous sublayer, it should be below 1 and for application of wall function it should be above 30. But what will be the accuracy of the result for y+ value in range of 5-25,i.e buffer region. From the Star-CCM+ user guide, I got to know about the Two layer all y+ wall treatment which basically switched between high Y+ and low Y+ wall treatment according to Y+ value. But what will happen when y+ value is between 5-25? Can Realizable k-epsilon model resolve it efficiently?

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February 26, 2016, 07:35		#2
Blanco Senior Member Blanco Join Date: Mar 2009 Location: Torino, Italy Posts: 193 Rep Power: 17	Short answer :no ;-) none of the rans turbulence models is appropriate in the buffer region, even if sometimes the high re approach could give good results also when y+ is as low as 11-15, but this is very case dependent.