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-   -   Need Assistance: BCs for k-e model implementation (http://www.cfd-online.com/Forums/main/3787-need-assistance-bcs-k-e-model-implementation.html)

Dean Schrage August 10, 2001 07:08

Need Assistance: BCs for k-e model implementation
 
Hi all

I am implementing a k-epsilon turbulence model in my general purpose CFD code. Here is the situation. The code engine employs an ADI-Brian solution to a general advective-diffusive transport equation. It is general because I port to the solver a vector of states and sources to derive a solution.

Q = [u,v,w,T,P] with sources, [P_x, P_y, P_z, Q, B] and respective diffusion coefficients

The pressure solution is derive by a parabolized extention of the PPE.

With this formulation I plan to port the additional [k, epsilon] states. I think I can figure out the source terms (they appear to be well documented). However the question is boundary conditions for [k, epsilon] states. My code engine can take on either standard Dirichlet or Neumann type BCs. I appear to be reading conflicting information on the type of BC for [k e].

I must stress that I am looking for something simple. Let's keep this easy. I have low Re numbers incompressible flows over obstructions. Generally I have defined velocity BCs for an inflow region (and zero for solid walls) and defined P-BC for an exit region. Dirichlet BCs for velocity force a Neumann BCs for pressure and vice versa. Given that what would you recommend for the BC formulation for k and e.

Thanks in advance.

Sebastien Perron August 10, 2001 08:21

Re: Need Assistance: BCs for k-e model implementat
 
Look for Reichardt law.

Or if can read french, I could send you Bc's and an algorithm for calculating the BC's.

John C. Chien August 10, 2001 14:37

Re: Need Assistance: BCs for k-e model implementat
 
(1).For turbulence modeling, please see David C. Wilcox book, "Turbulence Modeling for CFD". (2). Make sure that you understand the definition of k and epsilon. There are a couple of versions of epsilon being used. Also the nature of the equations require special attention in terms of solution procedure.

ssutikno August 11, 2001 01:02

Re: Need Assistance: BCs for k-e model implementat
 
Hi... Perron... I have same problem with Schrage, so if you don't mind please send me your Bc's and an algorithm for calculating the BC's. thank you...!!!

ssutikno


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