RSM implementation
 

Hy, mates.

Does anybody here have any experience at implementing a Reynolds-stress (second-moment) closure into a CFD code?

If positive, please, which were the numerical difficulties, and how were them solved? What are the tips for a robust implementation of such models into a numerical code?

Thanx in advance! Best regards, Biga

Re: RSM implementation
 

The most important parts of implementation of the second moment closure turbulence model are the introduction of the apparent viscosity, the source term linearization and the treatment of wall condition. These are well established now, especially by Lien and Leschziner. Read following papers by them.

(1) 'Numerical aspects of applying second-moment closure to complex flows' in "Closure strategies for turbulent and transitional flows" edited by Launder and Sandham, pp.153-187, Cambridge University Press, 2002. (there are some typing errors in Table 1)

(2) 'Second moment modelling of recirculating flow with a non-orthogonal collocated finite volume algorithm', in Turbulent Shear Flow 8, Springer, pp.205-222, 1993.

(3) 'A general non-orthogonal finite volume algorithm for turbulent flow at all speed incorporating second-moment closure, Part 1; Numerical implementation' in Comp. Meths. Appl. Mech. Engrg. 114, pp.123-148. 1994.

I hope this helps,

Haalim Choi

Re: RSM implementation
 

Thank you for replying!

Aren't the first two parts (apparent viscosity and source term linearization) only necessary in an implicit context? I'm currently working in an explicit (multistage Runge-Kutta) one.

My question is also more on implementation "dirty work" ;) , such as clippings, bounds etc that are necessary to (hopefully) control the time evolution of the Reynolds stresses. Just for information, I'm using the Batten, Craft and Launder model (Batten at. al, AIAA Journal, 99) low-Re RSM model in a compressible flow solver.

Thanx, Biga

Re: RSM implementation
 

Dear Biga;

(1) The works by Lien and Leschziner are based on the semi-implicit (so called SIMPLE) algorithm.

(2) I did not have any problems when I applied their method to natural, mixed and forced convection problems etc.

You can used their method for compressible flows together with the SIMPLE algorithm, see reference-3. As you pointed out well, however, their method is meaningless for explicit method.

Halim Choi.

Re: RSM implementation
 

I still couldn´t hand me those articles... it´s a bit hard to get them here in Brazil... ;)

Ok, the implicit treatments are meaningless for my explicit framework. There still is the wall BC treatment... but aren´t the reynolds stresses zero at the wall? Or does your "treatment of wall conditions" in your second reply mean other than BC, such as inhomogeinities pressure correlations and so on?

Thanx very much for the help! =D Biga

Re: RSM implementation
 

The wall boundary condition I am talking about is the treatment of Reynolds stresses near the wall when you use the wall function method in a nonorthogonal grid situation. If you uses the low-Reynolds number differential stress model, there is no problem.

Halim Choi