Large Eddy Simulation of turbulent mixing. 1st report Two-dimensional flow field.

Abstract

The aim of this study is a clarification of the relation between the coherent structure of a turbulent shear flow and turbulent mixing, especially the relation between the amalgamation of vortices and turbulent mixing. To achieve this purpose, Large Eddy Simulation of a turbulent shear flow with passive scalar mixing was conducted. As an initial value, a two-dimensional small perturbation was overlapped on the mean velocity profile. From the calculated results, without pairing of vortices, it was made clear that the gradient of the mean concentration profile changes in three stages, and that the turbulent mixing is enhanced by the vortical motion. From the calculated results with pairing of vortices, it was shown that the gradient of the mean concentration profile also changes in three stages, and an inversion of the concentration gradient is observed. From these calculated results, it was also made clear that the turbulent mixing is enhanced by pairing of the vortices.