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yPlus for LowRe-turbulence models

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Old   September 10, 2011, 04:50
Default yPlus for LowRe-turbulence models
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André Laß
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Hello FOAMers,
I am quite new to OpenFOAM and i want to use a LowRe-turbulence model without Wallmodelling like the LamBremhorstKE model for an impinging jet simulation.
Is there a way to calculate the yPlus-values to ensure that y+ is below 1 at every wall?

The utility yPlusRAS seems only to work with nutWallfunction in use.
I would be Grad if anyone could live a hint...
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Old   September 10, 2011, 05:07
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Felix L.
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Good morning, Andre,


you can estimate a cell height using a prescribed y+ with this tool:
http://geolab.larc.nasa.gov/APPS/YPlus/

On the other side, if you have experimental reference data available you can check it for measured wall shear stresses or even friction velocities to use for your estimation.


Greetings,
Felix.
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Old   September 10, 2011, 05:18
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André Laß
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Hello Felix,
Thanks for you hint according the estimation.
Do you know a way to compute the yPlus value at all near-wall nodes? Because I'd like to plot the yPlus value along the entire Wall using paraview.
Greetings,
André
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Old   September 10, 2011, 06:16
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Felix L.
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I suggest searching the forums for this, there are plenty of threads dealing with this topic.

You probably have to use the nutLowReWallFunction for nut at the wall patch and run yPlusRAS afterwards.


Greetings,
Felix.
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Old   September 10, 2011, 07:06
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André Laß
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[So you would say that the nutLowReWallfunction does not affect the solution when y+ is below 1? When using this wallfunction Do i have to use wallfunctions for k and epsilon too or can i set them to zero as default in lowRe-turbulence model?

Thanks for you help
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Old   September 10, 2011, 07:22
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Felix L.
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The nutLowReWallfunction is only a dummy wall function which effectively sets the eddy viscosity to zero at the wall (which is true for y+<5). The BCs for k and epsilon can be chosen independently and shouldn't be wall functions.


Greetings,
Felix.
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Old   September 10, 2011, 09:43
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André Laß
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Thank you every much for your help...
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