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June 9, 2012, 09:52 |
y+ in practice
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#1 |
Member
Robert
Join Date: Mar 2011
Location: Warsaw
Posts: 62
Rep Power: 15 |
Hello,
Recently I have started meshing some simple geometries for heat-flow problems. I have encountered something like y+ coefficient. I understand basics of theory for this but I still have problems with usage of this. How should I use it? If I have simple turbulent flow in a tube of given diameter how can I calculate mesh size for it using y+? Can anyone explain it to me in the easy way? |
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June 9, 2012, 10:09 |
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#2 |
Super Moderator
Ghazlani M. Ali
Join Date: May 2011
Location: Tokyo, Japan
Posts: 1,385
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This can help you a lot :
http://www.cfd-online.com/Forums/flu...-diffuser.html http://www.cfd-online.com/Forums/flu...h-correct.html If yous search the forum in the y+ you will find a lot of threads about it. |
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June 9, 2012, 13:53 |
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#3 |
New Member
Join Date: May 2012
Location: Moscow
Posts: 27
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I would also recommend reading this: http://tinyurl.com/bs6rla7
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June 9, 2012, 15:56 |
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#4 |
Member
Robert
Join Date: Mar 2011
Location: Warsaw
Posts: 62
Rep Power: 15 |
I am familiar with this article and OK, I understand for which turbulence what value of y+ should be used. But my question is how can I calculate size of the first cell next to the wall using this value and obtain size in mm?
I have found CFD Online y+ estimator and there is sth like boundary layer length - is this length of the entire boundary layer or just let's say length of the turbulent part? In the simple pipe will it be its length? |
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June 9, 2012, 19:33 |
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#5 |
Senior Member
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Y+ should not ideally lie in the range of 5 to 30.. this is where laminar to turbulence transition takes place.
It should not lie in this range bcos capturing physics in the transition layer is quite a task in itself. So i generally run the fluent for around 50 iterations and then check the Y+ value. If Y+ has to changed then i come back to my meshing software to redo the mesh as required (to either coarsen or refine)..may be you can try this procedure.. Concept of Y+ calculation can be read separately... |
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June 10, 2012, 09:51 |
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#6 | |
Member
Join Date: Nov 2011
Location: Czech Republic
Posts: 97
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Quote:
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meshing advice, y+ coefficient |
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