Direct Numerical Simulation of Nonequilibrium Effects on Decaying Isotropic Turbulence

Abstract

The Direct Numerical Simulation of decaying isotropic turbulence is performed with nonequilibrium effects. Oxygen is used as the test gas in the simulations. The individual and combined effects of vibrational relaxation and chemical reactions are studied by considering four different simulation cases. The time evolution of mean thermodynamic properties and turbulent statistics is analyzed. Budgets for turbulent kinetic energy and mean internal energy are computed to explain the dynamics of energy exchange associated with different nonequilibrium effects. The time evolution of enstrophy and turbulent length scales is also studied. The dissociation reaction is found to significantly affect the evolution of mean thermodynamic quantities as well as turbulence. Vibrational relaxation is found to significantly affect the flow in the presence of chemical reactions. The effects of changing the initial conditions on the resulting flowfield are analyzed.