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Limiting the production of turbulent kinitec energy

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Old   March 20, 2017, 01:20
Default Limiting the production of turbulent kinitec energy
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Hi all,

I am looking to best model vortices formed by a delta winged aircraft for an AoA range of -5 to 25 degrees using a steady state solver.

I have attached an excerpt of an AIAA paper I was reading (Integration of Multi-Fidelity methods for Generating an Aerodynamic Model for Flight Simulation), where they state:

"It is well known that most linear 2-equation turbulence models over-predict the eddy viscosity within vortex cores, thus causing too much diffusion of vorticity".

The referenced articles are:

Gordnier, R. E. “Computational study of a turbulent delta-wing flowfield using two-equation turbulence models”. AIAA 96-2076, 1996.

and a link to the second is:
http://reports.nlr.nl/xmlui/bitstrea...pdf?sequence=1

These both discuss the usage of a limiting term in the standard k-e and k-w models. I was wondering if anybody has any input on this topic or found this necessary when using either the realisable k-e or the SST k-w for similar simulations to mine.

Cheers.
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Last edited by tbwake; March 20, 2017 at 01:52. Reason: Add info
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Old   March 20, 2017, 06:18
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Hi,
I am also facing the similar problem my k-epsilon model, where I found I am over predicting the Production term and I followed "Turbulent Flows" by S.B. Pope for my studies. As the paper suggests limiting the production term, the Author of the book proves that the production term is actually bounded as (Exercise 5.21)
|P|<= 2*k*S(l).

k = Turbulent kinetic energy
S(l) is the largest absolute value of the eigenvalues of the mean rate-of-strain tensor.

I have not really tried limiting the production term till now because I am still studying whether the flow is stagnant there or not and should I limit the terms using explicit formulation of k.

Any discussion in this field will be helpful.

Thanks
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