Can i semulate a DNS in Star-CD and how if a can?

Detached Eddy Simulation and LES are possible for sure and more details can be found in the user manual

i know it, but DNS is not described in manual.

Its not possible with STAR-CD

DB

Or with any comercial package for that matter, they just aren't set up for such accuracy

Thank you very much.

DNS is possible with STAR-CD. DNS is where you do not use any turbulence modelling, you resolve everything with the grid. Therefore, you run laminar (or LES: it depends).

The "correct" approach is to run laminar - DNS = no turbulence model = laminar. NB: a laminar setting means no turbulence model, it does not mean that whatever scenario you apply it to will/must be laminar. Obviously, the problem being that if your flow really is turbulent and you run true-DNS/laminar, you'd better have a very large computer!

Alternatively, you could run LES. Because the subgrid scale contributions from LES's turbulence model are dependant on the cell size (filter length), if you refine your mesh enough, you end with a DNS solution. The advantages of this approach being: 1. if your mesh is too coarse you'll get a better answer, as the subgrid scale model will do its job; 2. it's likely to be more stable - one significant benefit of using a turbulence model is that they tend to stabalise the calculation.

I have used STAR-CD with the second approach and obtained excellent results as compared with experiment.

To run a calculation in a so called DNS mode is possible. I just add one more option to the ones given by Tim. Run in LES mode but with the model constant=0.0 then you will even have the statistics computed for you. However, to say that is a valid DNS this can be an open debate mainly due to the numerical dessipation.