Computation of Y+ is not correct

ghorrocks · February 28, 2014, 04:45

Why do you say DNS and RANS should match each other? They are very different approaches, so isn't some variation to be expected?

Lukas90 · February 28, 2014, 05:09

Of course it is, but I compared the results with some other and the result of RANS matched in all cases the DNS-data and the wall function. So I think my results should do the same.
I my thinking the first calculated y+ value should be identical with the exported y+ value for the first node. And that's why i came to this modification...

ghorrocks · February 28, 2014, 05:29

Your results are already pretty close so you know you are not far wrong. If you expect that you can get your results closer to the DNS line then you need to do a careful validation of mesh size, convergence and time step size.

Lukas90 · February 28, 2014, 05:36

OK I will try this suggestions.

Thank you very much for your help Garrocks.

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February 28, 2014, 04:45		#21
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 18,018 Rep Power: 146	Why do you say DNS and RANS should match each other? They are very different approaches, so isn't some variation to be expected?

February 28, 2014, 05:09		#22
Lukas90 New Member Join Date: Jan 2014 Posts: 13 Rep Power: 14	Of course it is, but I compared the results with some other and the result of RANS matched in all cases the DNS-data and the wall function. So I think my results should do the same. I my thinking the first calculated y+ value should be identical with the exported y+ value for the first node. And that's why i came to this modification...

February 28, 2014, 05:29		#23
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 18,018 Rep Power: 146	Your results are already pretty close so you know you are not far wrong. If you expect that you can get your results closer to the DNS line then you need to do a careful validation of mesh size, convergence and time step size.

February 28, 2014, 05:36		#24
Lukas90 New Member Join Date: Jan 2014 Posts: 13 Rep Power: 14	OK I will try this suggestions. Thank you very much for your help Garrocks.