2018 Volume 74 Issue 1 Pages 27-37
This is the first attempt to study the effects of mass density ratio on collision statistics in an isotropic particle-laden turbulent suspension. Previous studies have concentrated on the collisions of either the Lagrangian particles following the fluid motions completely or the inertial particles which is much heavier than the surrounding fluid. The present study is an extension of Yokojima et al. (J. JSCE A2 72(2) I_459 2016), where the influence of mass density ratio on clustering/preferential concentration of monodisperse small particles in a turbulent environment was examined closely by direct simulations of turbulent flows. It has been revealed from the present study that the collision frequency is increased with increase in the specific density, i.e., the ratio of the mass density of the particles on the fluid density, and that the primary factor is the local/instantaneous increase in particle number density owing to the particle clustering. The accuracy of the collision-frequency estimation model based on the radial relative velocity and the radial distribution function is also examined. The model prediction is found to be in excellent agreement with the simulation results.
