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Old   August 24, 2007, 06:13
Default Hi all, I'm working on a LowR
cosimo bianchini
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Hi all,
I'm working on a LowReynoldsNumber ReynoldsStressModel based on Wilcox's.
I just have a couple of questions regarding existing compressible RSMs.

1) I guess that laminar behavior and modeling is not affected by turbulence models selections. I mean that a non-turbulent case could always be modeled as turbulent with mut=0. And results should not be influenced by the choice of turbulent model.
So why divRhoR for RSM is returning:

fvc::div( rho_ * R_,"divRhoR")
- fvm::laplacian(muEff(), U)
+ fvc::laplacian(mut_, U)

resulting for a laminar case in

- fvm::laplacian(mu(), U)

that is not consistent with the other two equation models:
- fvm::laplacian(mu(), U) - fvc::div(mu()*dev2(fvc::grad(U)().T())) ?

Might it be a bug?
Possible fix:
fvc::div( rho_ * R_,"divRhoR")
- fvm::laplacian(muEff(), U)
+ fvc::laplacian(mut_, U)
- fvc::div(mu()*dev2(fvc::grad(U)().T()))

2) Are there any specific solvers for RSM?

3) How do you manage (I'm still working with OF-1.3 and I saw inthe new version this problem is oslved) the possibility for R to result non-symmetric?

4) How do you model turbulent heat flux?
divRhoUh does not seem to be implemented in neither Launder&Gibson nor LRR, so they still model isotropic turbulent heat flux. I would like to use Generalized Gradient Diffusion Hypothesis.
So my divRhoUh results to be:

- fvc::div(mut_* 3.3 *(R_ & tgradh())/k_,"divRhoUh")
+ fvc::laplacian(mut_* alphah, h)
- fvm::laplacian(alphaEff(), h)

I found constant 3.3 to be valid for flat plates (Ameri 2002).
Is there anyone who have already done it and could suggest me other expressions?

Thanks a lot for your time,
Cosimo Bianchini

Ergon Research s.r.l.
Via Panciatichi, 92
50127 Florence - ITALY
Tel: +39 055 0763716
Mob: +39 320 9460153
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