Numerical simulation of compressible homogeneous turbulence

The renewed interest in hypersonic flight has fostered a need to increase our understanding of turbulence and mixing in high Mach number flows. The objective of this work is to aid the development of turbulence models for compressible flows by using direct numerical simulations of compressible homogeneous turbulence. The present study focuses on decaying isotropic turbulence and homogeneous shear flow.; The numerical simulations of compressible isotropic turbulence show that compressibility effects are highly dependent on the initial conditions. For this reason, decaying compressible isotropic turbulence is difficult to model.; The shear flow simulations, on the other hand, show that the measures of compressibility evolve to become independent of their initial values and are parameterized by the rms Mach number. Therefore, simulations of homogeneous shear flow are especially useful in evaluating compressibility effects.; The growth rate of the turbulence in compressible homogeneous shear flow is reduced compared to that in the incompressible case. This behavior is similar to that observed for compressible mixing layers. The reduced growth rate is the result of an increase in the dissipation rate of turbulent kinetic energy due to the divergence of the velocity. In addition, kinetic energy is transferred to pressure fluctuations by the pressure-dilatation correlation.; Examination of the structure of compressible homogeneous shear flow reveals the presence of eddy shocklets. These structures are important for the increased dissipation rate of compressible turbulence.; The simulations included a passive scalar so that mixing could be studied. The major finding concerning passive scalar transport is that the dilatational velocity does not contribute to mixing. This result indicates that compressible turbulence is less efficient at mixing than incompressible turbulence.