Decay Process of Three-Dimensionally Anisotropic Turbulence.

Abstract

Homogeneous three dimensionally anisotropic turbulence with extremely large anisotropy was generated in a wind tunnel. Early in the return-to-isotropy process, pancake-shaped anisotropic turbulence evolved into a cigar-shaped axisymmetric one and then decayed into quasi-isotropic turbulence. The ratio of the rate of energy dissipation to that of return to isotropy, α, changed stepwise in each stage of the return-to-isotropy process. Such an aspect in the change of αwas related to the streamwise variations of the anisotropy tensor and turbulence intensity and to the restoration of energy defects in the one-dimensional spectra. The anisotropy invariant map showed that Sarkar's quadratic nonlinear model gave a better prediction for the return-to-isotropy process of turbulence with large anisotropy.