Particle turbulent diffusion, bias, and modulation

This work reviews recent advances in turbulent diffusion of particles, the bias effects of turbulence on particle velocity, and the effects of particles on turbulence. Based on the Hinze’s theory of particle motion for a theoretical kinetic energy spectrum, turbulent diffusion as well as absolute and relative particle velocity fluctuations can be related to directional particle Stokes numbers at the microscale and integral scale for a broad range of inertias and drift parameters. The influence of turbulence can also lead to biases on the mean particle motion and these include non-linear drag bias, preferential bias, clustering bias, diffusiophoresis, and turbophoresis. These effects can be considered individually to show their controlling parameters and it is often reasonable to linearly combine their effects (as demonstrated by comparison with experimental and computational results). Lastly, predicting turbulence modulation has generally proved very difficult, but a new length-scale approach based on turbulent dissipation is found to predict trends for flows that are nearly homogenous and isotropic as well as for pipe flows.