Simulation and modeling of turbulence subjected to a period of axisymmetric contraction or expansion

Abstract

The effect of axisymmetric contraction and expansion on isotropic turbulence and its subsequent decay are evaluated by way of direct numerical simulation. Low, moderate, and high rates of contraction and expansion are evaluated at a moderate Reynolds number using two different sets of initial conditions of isotropic turbulence. The initial turbulence is generated via mechanical mixing so that the large scales of the turbulence develop naturally. Length scales, decay rates, anisotropy, and twopoint correlations are investigated both during and after the straining process, with the goal of quantifying how anisotropic turbulence behaves during return-to-isotropy.