y+ check in k-w and k-e model

vaina74 · March 30, 2010, 07:20

My case concerns the blade section of a marine propeller and the Reynolds number is about 1.9E6. I applied the k-w SST model, then I'll use the k-e turbulent model. I'm a beginner, so I want to check the near-wall mesh refinement. I used the yPlusRAS utility:

Patch 3 named wall y+ : min: 7.41589 max: 18.6215 average: 16.7689

How can I check the correctness of the mesh? I'm not sure of the y+ criteria about the boundary layers.

A.Devesa · March 30, 2010, 09:01

if you want to be wall-resolved, then you should have a y+ of the order of one and use the "low Reynolds" models instead of the models you mentioned.

for "high Reynolds" turbulence models, your wall resolution is already pretty much fine, you could even coarsen it up a bit, up to let's say 30~50...

vaina74 · March 30, 2010, 13:43

Can you explain me the yPlusRAS utility result?

y+ : min: 7.41589 max: 18.6215 average: 16.7689

Does it mean that each wall-adjacent first cell centroid is located within the log-law layer, 7.4 < y+ < 18.6?

A.Devesa · March 31, 2010, 05:07

well your yPlusRAS results say that you are in the buffer layer, which roughly extends from ~3 to ~30. So your first off-wall points are neither in the viscous layer nor in the log layer.

vaina74 · April 1, 2010, 09:01

Sorry, i meant buffer and not log layer

I just wasn't sure about the meaning of the YPlusRAS and the link between the utility and my first off-wall points. Thank you,Antoine.

March 30, 2010, 07:20	y+ check in k-w and k-e model	#1
vaina74 Senior Member Join Date: Feb 2010 Posts: 213 Rep Power: 17	My case concerns the blade section of a marine propeller and the Reynolds number is about 1.9E6. I applied the k-w SST model, then I'll use the k-e turbulent model. I'm a beginner, so I want to check the near-wall mesh refinement. I used the yPlusRAS utility: Patch 3 named wall y+ : min: 7.41589 max: 18.6215 average: 16.7689 How can I check the correctness of the mesh? I'm not sure of the y+ criteria about the boundary layers.

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March 30, 2010, 09:01		#2
A.Devesa Member Antoine Devesa Join Date: Mar 2010 Posts: 36 Rep Power: 16	if you want to be wall-resolved, then you should have a y+ of the order of one and use the "low Reynolds" models instead of the models you mentioned. for "high Reynolds" turbulence models, your wall resolution is already pretty much fine, you could even coarsen it up a bit, up to let's say 30~50...

March 30, 2010, 13:43		#3
vaina74 Senior Member Join Date: Feb 2010 Posts: 213 Rep Power: 17	Can you explain me the yPlusRAS utility result? y+ : min: 7.41589 max: 18.6215 average: 16.7689 Does it mean that each wall-adjacent first cell centroid is located within the log-law layer, 7.4 < y+ < 18.6?

March 31, 2010, 05:07		#4
A.Devesa Member Antoine Devesa Join Date: Mar 2010 Posts: 36 Rep Power: 16	well your yPlusRAS results say that you are in the buffer layer, which roughly extends from ~3 to ~30. So your first off-wall points are neither in the viscous layer nor in the log layer.

April 1, 2010, 09:01		#5
vaina74 Senior Member Join Date: Feb 2010 Posts: 213 Rep Power: 17	Sorry, i meant buffer and not log layer I just wasn't sure about the meaning of the YPlusRAS and the link between the utility and my first off-wall points. Thank you,Antoine.