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June 12, 2012, 11:07 |
y+ wide range 0.5 - 90
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#1 |
Senior Member
Join Date: May 2011
Location: Germany
Posts: 130
Rep Power: 14 |
Hi,
I am facing new problem with a new meshing tool. When I run my simulation I get a wide range of y+ (0.5 - 90). My problem now is which wall function should I use. I am using realizable k-epsilon.... I know, that for standard wall function y+ should be in the range of 30.... 300. But can enhanced wall function handle my problem? I can handle the y+ value at the area where I am most interested, but not for the whole mesh. Hope you guys have any advice. Thanks in advance |
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June 13, 2012, 11:23 |
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#2 |
Member
Yon Han Chong
Join Date: Jun 2012
Posts: 77
Rep Power: 13 |
Are you doing a heat transfer calculation?
Why not run both the standard and enhanced wall treatment and compare the result. At the same time try the k-omega (which has an enhanced wall treatment built in) and compare the results as well. |
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June 13, 2012, 11:30 |
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#3 |
Senior Member
Join Date: May 2011
Location: Germany
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Yes I am running heat transfer.
Experience with realizable k-epsilon are quite good so far. I just wanted to check I the results are bad anyway because I can not meet y+>30 for the standard wall function ... so it might not be reasonable to run the simulation at all! What about k-w? Is there no limit for the y+ range and wall funtions? I don't think so .... |
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June 13, 2012, 12:00 |
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#4 |
Member
Yon Han Chong
Join Date: Jun 2012
Posts: 77
Rep Power: 13 |
My experince is that k-w seems to handle wider y+ better than k-e for heat transfer. I would still run it (considering how long it take to generate error free prism mesh) but would compare all three results as rerunning with different turbulence models that much.
Last edited by yonchong; June 14, 2012 at 10:33. |
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June 13, 2012, 12:52 |
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#5 | |
New Member
Join Date: Nov 2011
Posts: 27
Rep Power: 14 |
Quote:
Fluent's guide recommends to use the realizable k-epsilon turbulence model with the enhanced wall functions for meshes with y+ close to 1. The application of the standard wall function will not provide good results, I guess. For the k-omega model, the default wall function is the same as the k-epsilon enhanced wall function. I believe that would be interesting for you to run these both cases: k-epsilon with enchanced wall function and then using k-omega. |
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June 14, 2012, 02:19 |
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#6 |
Senior Member
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Probelm is, that I can not get y+ values close to 1 at my traget surface ...
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June 14, 2012, 04:00 |
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#8 |
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June 14, 2012, 05:03 |
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#9 |
Super Moderator
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through text user interface. It is only available for Epsilon based models.
However, in K-W model (at-least true for Fluent 14) it automatically changes to integration to wall approach to standard wall function according to following scheme: Below 6 : integration to wall. Between 6 and 30 : mix of both with blending factor. above 30: standard wall function. However for heat transfer calculation you should consider the appropriate range of thermal Y+ to accurately heat transfer. |
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June 14, 2012, 05:20 |
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#10 |
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Location: Germany
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June 14, 2012, 06:01 |
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#11 |
Super Moderator
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Quote from Fluent Guide
Scalable wall functions can be enabled only when the standard wall functions are used and only via the following text command: define/models/viscous/near-wall-treatment/scalable-wall-functions? https://www.sharcnet.ca/Software/Flu.../th/node99.htm https://www.sharcnet.ca/Software/Flu...list/fltui.pdf |
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June 14, 2012, 10:36 |
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#12 |
Senior Member
Join Date: May 2011
Location: Germany
Posts: 130
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Thanks a lot!
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