RIGOROUS MODELING OF DISSIPATION-RATE EQUATION USING DIRECT SIMULATIONS

With the aid of direct numerical simulation (DNS) data, we have constructed near-wall modeling of the dissipation-rate equation for a kappa-epsilon turbulence model. All the budget terms in the exact epsilon-equation are incorporated in the modeled epsilon-equation, and both term-to-term and overall comparisons of model predictions with the DNS data are performed. It is found that the wall region should be partitioned into at least two regions so as to reflect different mechanisms of the generation processes in the dissipation of turbulent kinetic energy. Pressure diffusions in the kappa- and epsilon-equations are found to be equally important and thus should be modeled. Comparisons of the resultant kappa-epsilon model with the DNS data of channel and boundary layer flows with and without pressure gradients show close agreement of various turbulent quantities. In particular, near-wall behavior of epsilon is reproduced with the present model very well.