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nut and nuTilda

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Old   August 29, 2013, 10:10
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vishal
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Hello Everyone, did u got the correct interpretation for X??
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Old   October 18, 2013, 07:26
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Hello Everyone, did u got the correct interpretation for X??
Same, question here, and how to calculate it from freestream turbulence properties!
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Old   July 15, 2014, 03:15
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well X is specified as nutilda/nu, nutilda as zero on walls and aswell zero in the free stream, but for stability reasons values fo nutilda < 0.5 nu can be applied. In case you only need it as a starting value (and I think this is the case for Hybrid URANS_LES DES, DDES using Spalart-Allmaras) wikipedia suggests to use nutilda = 5nu in the free stream, which causes turbulence to develop whereever shear flow occurs. (see http://www.cfd-online.com/Wiki/Turbu...ary_conditions)
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Old   November 6, 2014, 05:27
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what value i have to mention in nut file for outlet
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Old   November 29, 2014, 22:34
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since you already got it, could you please share it.

Regards,
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Old   December 31, 2014, 19:55
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I was really confused since the nuTilda file exists even with kEpsilon models in the tutorial. Now I know it is superfluous.

Thank you, guys!

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nut> dynamic turbulence viscosity
nutilda> kinamatic turbulence viscosity

aren't they?

and what is the different ?
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Old   January 4, 2015, 21:54
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nut> dynamic turbulence viscosity
nutilda> kinamatic turbulence viscosity

aren't they?

and what is the different ?
The field "nuTilda" is a pseudo turbulent viscosity, which is solved for through a transport equation in all Spalart-Allmaras based turbulence models (be it SA-RANS or any of the SA-DES models).

The field "nut" is the actual "turbulent viscosity" and is proportional to "nuTilda" by the fv1 function, where fv1 is locally a function of the viscosity ratio nuTilda/nu.

One should always initialize the field "nuTilda" appropriately.
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Old   April 22, 2016, 04:30
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Dear Albrecht,

A quick question about initializing nut from nuTilda (SA model) in OpenFOAM3.0.1. Should I include a nut file in 0/ directory with values calculated manually from nuTilda? (using fv1 and Cv1) or, will OF generate nut files automatically once the simulation runs?

Usually, to be on the safe side, I would initialize the nut file manually in 0/, but I was just wondering if that may create any conflict with OF as the way of dealing with some algorithms may change between versions.

Thanks!
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