Compressibility effects in modeling complex turbulent flows

The effect of compressibility on the structure of turbulence is an important, but difficult, topic in turbulence modeling. Modeling issues in production, dissipation and transport of turbulent kinetic energy need to be addressed to account for Mach number effects. In the present review, the compressibility effect is investigated in the context of engineering models needed for complex flow computations, particularly the k-ε model. Issues such as the dissipative nature of compressibility, the complexities arising due to the non-divergent nature of the velocity field, added time-scale effect due to a non-equilibrium between the rates of production and dissipation of turbulent kinetic energy, the enthalpic production term and the term representing the baroclinic effect, have been discussed to facilitate the inclusion of these terms in the solution of compressible turbulent flow fields. Flows characterized by strong streamline curvature and inhomogeneities arising due to strong shocks and rapid expansions, in the form of supersonic flow past an axi-symmetric afterbody and hypersonic flow past a projectile, have been adopted to facilitate computational assessment of these aspects.