Thermodynamics induced compressibility in high-pressure shear flows

Turbulence at high pressures, exceeding the species critical value, determines mixing/combustion in various propulsion devices. At such pressures, the thermodynamic conditions induce real gas compressibility, in contrast to the dynamics-based compressibility that is commonly quantified by the convective or the turbulence Mach number. The real gas compressibility modifies the dilatation of a fluid element in response to a pressure fluctuation resulting in pressure-strain correlations and Reynolds stress anisotropy that is different from an ideal gas. The extent of the modification depends on the flow dynamics (the shear rate) as well as the thermodynamics (the pressure/temperature conditions). This study uses compressible homogeneous shear flow simulations to investigate the mechanism by which high-pressure conditions influence flow turbulence. The transport equations for the r.m.s. velocity fluctuations and the pressure variance are assessed to examine turbulent energy growth at various shear rates, turbulence Mach numbers, and pressure conditions. The implications on subgrid-scale modeling of such flows will be discussed.