Scalar Statistics along Inertial Particle Trajectory in Isotropic Turbulence

Abstract

In this paper, statistics of passive scalar along inertial particle trajectory in homogenous isotropic turbulence with a mean scalar gradient are investigated by using of direct numerical simulation, and the prime interest is the influence of particle inertial on such statistics. The results show that, the scalar variance along particle trajectory behaves differently, it decreases with the increasing of Stokes number when the Stokes number less than 1.0, then increases if Stokes number increases further, and reaches the minimal value, at Stokes number around 1.0. The scalar dissipation rate, however, shows completely contrary behavior to scalar variance. The correlation between scalar dissipation and flow structure characteristics, such as strain and vorticity, along particle trajectory were also calculated and its corresponding correlation coefficients keep nearly 0.3 and 0.25 respectively. The mechanical to thermal time scale ratios along particle trajectory, which are important in Lagrangian model of scalar mixing, were also computed and keep nearby 1.77.