In sandstorms and thunderclouds, turbulence-induced collisions between solid
particles and ice crystals lead to inevitable triboelectrification. The charge
segregation is usually size-dependent, with small particles charged negatively
and large particles charged positively. In this work, we perform numerical
simulations to study the influence of charge segregation on the dynamics of
bidispersed inertial particles in turbulence. Direct numerical simulations of
homogeneous isotropic turbulence are performed with the Taylor Reynolds number
Reλ​=147.5, while particles are subjected to both
electrostatic interactions and fluid drag, with Stokes number of 1 and 10 for
small and large particles, respectively. Coulomb repulsion/attraction are shown
to effectively inhibit/enhance particle clustering within a short range.
Besides, the mean relative velocity between same-size particles is found to
rise as the particle charge increases because of the exclusion of low-velocity
pairs, while the relative velocity between different-size particles is almost
unaffected, emphasizing the dominant roles of differential inertia. The mean
Coulomb-turbulence parameter, Ct0​, is then defined to characterize
the competition between the Coulomb potential energy and the mean relative
kinetic energy. In addition, a model is proposed to quantify the rate at which
charged particles approach each other and captures the transition of the
particle relative motion from the turbulence-dominated regime to the
electrostatic-dominated regime. Finally, the probability distribution function
of the approaching rate between particle pairs are examined, and its dependence
on the Coulomb force is further discussed using the extended Coulomb-turbulence
parameter.Comment: 23 pages, 8 figure