Passive scalar characteristics along inertial particle trajectory in turbulent non-isothermal flows

Abstract

The momentum and heat coupling between carrier fluid and particles are a complex and challenge topic in turbulent reactive gas-solid flow modeling. Most observations on this topic, either numerical or experimental, are based on Eulerian framework, which is not enough for developing the probability density function (PDF) model. In this paper, the instantous behavior and multi-particle statistics of passive scalar along inertial particle trajectory, in homogenous isotropic turbulence with a mean scalar gradient, are investigated by using the direct numerical simulation (DNS). The results show that St∼1.0 particles are easy to aggregate in high strain and low vorticity regions in the fluid field, where the scalar dissipation is usually much higher than the mean value, and that every time they move across the cliff structures, the scalar change is much more intensive. Anyway, the self-correlation of scalar along particle trajectory is significantly different from the velocities observed by particle, for which the prefer-concentration effect is evident. The mechanical-to-thermal time scale ratio averaged along the particles, p, is approximately two times smaller than that computed in the Eulerian frame r, and stays at nearly 1.77 with a weak dependence on particle inertia.