Reynolds Stress Models

Jens Bennetsen

Hi,

I just fell over "Do we need LES for ventilations problems"

Yes sometimes we do !

I am doing research in ventilation problems in animal houses and using LES. Since many ventilation problems do involve low Reynolds number flow, where the tranditional turbulence do not predict the flow well, due to the transition between laminar and turbulent region. In this range LES is one of the only ways to proceed and furthermore traditionals turbulence often have problem predicting the right level of turbulence intensity and even semi-steady flow like a swicth-over from one side wall to the other. But in low Reynolds flow it is also difficult to make good measurement of the turbulent intensity.

Using LES is expensive, but an efficient implementation can reduce the computational demands very much. In fact LES is more about grid density, numerical method and implementation than chossing the rigth dynamic subgrid scale model, since we are modelling engineering flow problems, not basic block building flow like backfacing step and channel flows.

Best Regards

Jens