y+ wide range 0.5 - 90
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 |
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. |
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 .... |
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.
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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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use scalable wall function. It will discard the yplus values below 11.06.
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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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define/models/viscous/near-wall-treatment ??? or define/models/viscous/turbulence-expert/low-re-ke ??? Thanks |
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 |
Thanks a lot!
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