MODELING OF RAPID PRESSURE STRAIN IN REYNOLDS-STRESS CLOSURES

The most general form for the rapid pressure-strain rate, within the c ontext of classical Reynolds-stress transport (RST) closures for homog eneous flows, is derived, and truncated forms are obtained with the ai d of rapid distortion theory. By a classical RST-closure we here denot e a model with transport equations for the Reynolds stress tensor and the total dissipation rate. It is demonstrated that all earlier models for the rapid pressure-strain rate within the class of classical Reyn olds-stress closures can be formulated as subsets of the general form derived here. Direct numerical simulations were used to show that the dependence on flow parameters, such as the turbulent Reynolds number, is small, allowing rapid distortion theory to be used for the determin ation of model parameters. It was shown that such a nonlinear descript ion, of fourth order in the Reynolds-stress anisotropy tensor, is quit e sufficient to very accurately model the rapid pressure-strain in all cases of irrotational mean flows, but also to get reasonable predicti ons in, for example, a rapid homogeneous shear flow. Also, the respons e of a sudden change in the orientation of the principal axes of a pla ne strain is investigated for the present model and models proposed in the literature. Inherent restrictions on the predictive capability of Reynolds-stress closures for rotational effects are identified.