How is yplus calculated in OF?

jdd82 · March 18, 2010, 15:22

Can someone offer some insight into what OF does when you calculate "yPlusRAS"? When I view the output "y" (distance from the wall) in Paraview, the numbers look right. When I plot "yplus", it seems to only give me one non-zero value at the node closest to the wall. Also, I can't seem to figure out how it exactly arrives at that number - does it use u_tau = sqrt(k)*C_mu^0.25 (where k is the turbulent kinetic energy)? If so, which value of k does it use? The value at the node nearest to the wall?

I apologize if this was posted elsewhere but I couldn't find any specific info on it and it was a bit unclear looking in the source code.

jdd82 · March 22, 2010, 08:24

Bump. Any input?

sandy · March 27, 2010, 22:07

Yes, good method to output from parafoam.

louisgag · May 19, 2010, 11:20

Quote:

When I plot "yplus", it seems to only give me one non-zero value at the node closest to the wal

Similar situation here, yPlusRas outputs values for yPlus on my wall that seem to make sense but when I plot with paraview the values are different.

For example yPlusRas outputs

Code:

y+ : min: 0.300666258352 max: 4.7795851505 average: 2.08585637331

and paraview shows me values of yPlus that go from 0.002 to 78, which doesn't make sense considering my mesh resolution and velocity at wall are fairly constant...

EDIT: the error seems to come from the yPlus file that is being written.

sandy · May 19, 2010, 19:37

How to give the yplus to multiphase flows, it seems that values in multiphase pattern and single phase pattern are different to the wall turbulence. Who can give some light? Thanks.

March 18, 2010, 15:22	How is yplus calculated in OF?	#1
jdd82 New Member Join Date: Mar 2010 Posts: 2 Rep Power: 0	Can someone offer some insight into what OF does when you calculate "yPlusRAS"? When I view the output "y" (distance from the wall) in Paraview, the numbers look right. When I plot "yplus", it seems to only give me one non-zero value at the node closest to the wall. Also, I can't seem to figure out how it exactly arrives at that number - does it use u_tau = sqrt(k)*C_mu^0.25 (where k is the turbulent kinetic energy)? If so, which value of k does it use? The value at the node nearest to the wall? I apologize if this was posted elsewhere but I couldn't find any specific info on it and it was a bit unclear looking in the source code.

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March 22, 2010, 08:24		#2
jdd82 New Member Join Date: Mar 2010 Posts: 2 Rep Power: 0	Bump. Any input?

March 27, 2010, 22:07		#3
sandy Senior Member Sandy Lee Join Date: Mar 2009 Posts: 213 Rep Power: 18	Yes, good method to output from parafoam.

May 19, 2010, 19:37		#5
sandy Senior Member Sandy Lee Join Date: Mar 2009 Posts: 213 Rep Power: 18	How to give the yplus to multiphase flows, it seems that values in multiphase pattern and single phase pattern are different to the wall turbulence. Who can give some light? Thanks.