nonlinear kepsilon model implementation problems
I am currently working on implementaion of a nonlinear keps model in an inhouse code (a FVM code) which was originally written for linear EVM models. I can calculate Reynolds stresses pretty well with the explicit ASM model when I am still using linear EVM. It was just a check for me to see if there was any problem with Reynolds stress calculation. It showed that there is not. But when I try to put gradients of those calculated Reynolds stresses as source terms in the momentum equations and skip eddy viscousity concept, I got ckekerboard problem and instability. I have been familiar with the problem and so I tried ObiPericScheuerer's method (AIAA J., Vol. 29, No.4, 1991, pp. 585590), but I have still the same problem. If there is anyone out there who actually done this kind of coding work, I will be most grateful if he/she shares some of his/her experiences with me.

Re: nonlinear kepsilon model implementation problems
Hello! I have done some coding of nonlinear kepsilon models into the commercial CFD code CFX4. I implemented it into the standard keps treatment of CFX, separating the stressstrain relation into two parts. The first part is the standard linear term (already implemented in the code), the second part is the HOT (higher order terms, which can be quadratic or cubic or whatever). After calculating the HOT in the momentum equations, the appropriate gradients of these are added as source terms. This worked fine for me.
Anders 
Hello Saidi!
Do you have any reference for the nonlinear kepsilon modell? Cheers, Claus 
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