Effect of Compressibility on the Turbulence Structure and its Modeling.

In the present study, the compressibility effect is investigated in the context of the two-equation k-epsilon model. Several models have been proposed to deal with the dissipative nature of compressibility and the complexities arising due to the non-divergent nature of the velocity field. In addition modifications have been proposed to address the added time-scale effect that is due to a non-equlibrium between the rates of production and dissipation of turbulent kinetic energy in complex flows. The reduced dependence, of the k-omega based models on the spatial gradients in density, has been shown to be an artifact of the neglect of cross-diffusion terms in the transport equation for omega. Through a systematic study of the exact form of the turbulence transport equations two additional source terms that are unique to compressible turbulent flows, namely the enthalpic production term and the term representing the baroclinic effect, have been identified and models are proposed.