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July 13, 2016, 08:35 |
Boundary layer issues
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#1 |
New Member
Join Date: Apr 2016
Posts: 7
Rep Power: 9 |
Hello dear freinds,
I am modelling a De-laval Nozzle flow with K-e model and i am very suspicious about the velocity at the Wall. I've read the FAQ and the manual about hybrid and conservative values but i would like to hear some opinion. According to the Y+ values(<1) my near Wall mesh is fine enough, the Residuals also look good in all the Volume. The velocity in the centre of the flow is as expected 1350 m\s but the conservative value at the Wall is 650 m\s. Can it be that the gradien of the velocity in the first nearwallelement is so high that the averege nearwallelement velocity is 650 m\s. Tried to make the first nearwallelement even thinner the velocity just slightly decreases. Would be very thankfull and have a nice day! |
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July 13, 2016, 16:27 |
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#2 | |
Senior Member
Join Date: Jun 2009
Posts: 1,804
Rep Power: 32 |
As initial advice, it makes no sense to use meshes with Y+ < 11 for K-Epsilon model. Meshes with very small Y+ are meant to be used with Omega based models, either K-Omega, SST or similar.
For meshes with Y+ < 11, ANSYS CFX uses a scalable wall function and you can read the details in the documentation From the documentation: Quote:
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July 14, 2016, 04:53 |
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#3 |
New Member
Join Date: Apr 2016
Posts: 7
Rep Power: 9 |
Thank you very much! Than helped so much! Have a nice day!
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