Acoustic energy exchange in compressible turbulence

Abstract

The mechanism of exchange of kinetic energy and internal energy in a three-dimensional forced compressible turbulence is investigated by the analysis of a direct numerical simulation data. The Helmholtz decomposition of ρrlxu (ρ is the density of a fluid and u is the velocity), which yields positive–definite spectra of the compressive and rotational kinetic energies, is employed for exploring the relative importance of various terms in the kinetic energy equation. It is shown that the pressure–dilatation term makes a dominant contribution to the exchange of compressive kinetic energy and internal energy. This exchange occurs periodically at all wave numbers, the period of which is inversely proportional to the wave number. This indicates that acoustic waves take part in the exchange of energy.