Difference of Statistics between Compressible and Incompressible Turbulent Channel Flows.

Abstract

The difference of turbulent statistics between compressible and incompressible turbulent channel flows is investigated using the DNS data of the compressible turbulent channel flow between isothermal walls and the DNS data of the incompressible turbulent channel flow. For comparison of compressible and incompressible flows, the dependence of turbulent statistics on the semi-local friction Reynolds number Re*τ and the wall friction Reynolds number Reτ is clarified in the compressible and incompressible turbulent flows, respectively. The semi-local friction Reynolds number is based on the local density and viscosity, semi-local friction velocity, and channel half-width. The main results of this paper are as follows: (1) The dependence of the turbulence intensities of the wall-bounded compressible turbulent flow on Re*τ is almost the same as that of the incompressible turbulent flow on Reτ except for the streamwise turbulence intensity near the wall. The streamwise intensity depends on the Mach number. (2) The reduction in the pressure-strain correlation term suppresses the energy transfer from the streamwise component to the wall-normal and spanwise components. As a result, the streamwise turbulence intensity becomes larger, and the wall-normal and spanwise turbulence intensities become smaller in the compressible turbulent channel flow, comparing with the incompressible one. (3) The reduction in the pressure-strain correlation term is due to the reductions of the RMS velocity derivative fluctuations and the absolute values of correlation coefficients between pressure and velocity derivative fluctuations.