Particle-resolved direct numerical simulation of collisions of bidisperse inertial particles in a homogeneous isotropic turbulence

Abstract

A particle-resolved study of a collision system composed of heavy particles and light particles in a homogeneous isotropic turbulence has been performed. Direct numerical simulations (DNS) of this system were conducted using lattice Boltzmann method (LBM). The effects of hydrodynamics on the collision particles were accounted by directly resolving the flow around finite-size particles with an interpolated bounce-back scheme. A large-scale stochastic forcing scheme was implemented within the mesoscopic multiple-relaxation-time LBM approach to maintain turbulence intensity at targeted levels. Both kinematic and dynamic collision kernels were evaluated to study the correlation of total collision events and turbulent kinetic energy (TKE) dissipation rate. The results show that collisions between particles increase with the increase of TKE dissipation rate as radial relative velocities between particles increase with it. It is found that the dynamic collision kernels do not match with the kinematic collision kernels which is derived from point-particle method. Quantitatively, they were approximately 4 to 10 times smaller than the corresponding dynamic collision kernels. Therefore, it is not reasonable to estimate the kinematic collision kernel in particle-resolved simulations as its rationales are not valid. However, the collision behavior can still be accounted for by means of the dynamic collision kernel since it is obtained from the direct statistical analysis of the collision events.