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-   -   Re: Coupled solver + RNG K-e Model (http://www.cfd-online.com/Forums/fluent/28459-re-coupled-solver-rng-k-e-model.html)

JN April 22, 2001 11:57

Re: Coupled solver + RNG K-e Model
 
Hi, i hoper that somebody can help me. I'm trying to use the coupled explicit solver for compressible steady flow simulation over a turbine blade. I have selected RNG as tubrulence model. (i)what is the species diffusion? is it automatically computed in the energy transport? (ii)my problem is steady but the coupled solver uses a 5-stage runge kutta temporal scheme to converge the solution. so is the porblem still considered as unsteady until convergence is met?? if yes does this mean the judging convergence shall be done based on stablising quantities such as lift and drag ( not on x,y,z, velocity components etc...)???? (iii) as the flow is compressible does it use a favre averaged navier-stokes method to deal with turbulence or does the renormalisation technique provide a new set of equations derived directly from the instantaneous ones? (iv) is RNG an isotropic turbulence model?

thanks for replying JN

Kuochen Tsai April 22, 2001 16:34

Re: Coupled solver + RNG K-e Model
 
(i) Eddy diffusivity. And yes, it is computed in energy transport. (ii) Yes and no. Yes it is considered unsteady, but not time accurate at all, it is a psudo-time approach. And yes, solution is good only when stable quantitied are obtianed (iii) Favre -average is used for compressible flows. No. (iv) Yes, RNG is based on the same principle as k-e and is a isotropic model.


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