Motions of Small Rigid Spheres in Simulated Random Velocity Field

Abstract

Motions of particles in a simulated three‐dimensional random Gaussian flow field are numerically studied. The equation of motion of a solid particle (the generalized BBO equation), in addition to the Stokes drag, the Basset force, and the virtual mass effects, includes the three‐dimensional lift force. An ensemble of 300 particle trajectories are generated for evaluating various statistics. Turbulent diffusivity of small particles is calculated and its variations with nondimensional particle size, particle Reynolds number, density ratio, and particle response time are studied. Particle velocity autocorrelations and particle velocity‐fluid velocity cross‐correlations, as well as fluctuation energy transport from the fluid phase to the particulate phase, are evaluated. A simplified model for evaluating the particle response statistics is also described. The simulation results are compared with the predictions of the simplified model and the available experimental data and good agreement is observed. Effects of turbulence length scale, particle size, and density on particle diffusivity and various correlations and energy transports are also studied and discussed.