Algebraic turbulent energy flux models for hypersonic shear flows

Algebraic truncation models were derived for the turbulent energy flux for high-speed shear flows with and without thermal and mechanical non-equilibrium effects. To facilitate closure, fluctuating dilatation moments were modeled via conservation of mass truncations and the inhomogeneous terms were neglected. The resulting energy flux model provided significant improvements, up to 20%, in the temperature predictions over the gradient diffusion model for equilibrium flows over a Mach number range of 0.02-11.8. Our experiments showed that vibrational relaxation significantly altered the basic decay rate of grid turbulence. Also, our models indicated that compressibility introduces an explicit pressure gradient dependency. Analyses of a governing parameter indicated that these terms are negligibly small for low speeds, but may be important, or even dominant, for high-speed flows. (C) 2009 Elsevier Ltd. All rights reserved.