Electric field effects on the collision efficiency of uncharged water droplets in a linear flow

We study the dynamics of collisions between a pair of uncharged conducting droplets under the influence of a uniaxial compressional flow and an external electric field. The near-field asymptotic expression for the electric-field-induced attractive force demonstrates that surface-to-surface contact in finite time is facilitated by overcoming lubrication resistance. We demonstrate the significant role of the external electric field on the relative trajectories of two droplets in a compressional flow and provide estimates of the correlation between collision efficiency and the forces induced by the electric field. For droplet collisions in clouds, continuum lubrication approximations become inadequate to capture collision dynamics, and thus we incorporate noncontinuum lubrication interactions into our analysis to address this complexity. Our findings reveal the dependence of collision efficiency on the strength of the electric field, geometry of the two interacting droplets, noncontinuum effects, and van der Waals forces. We show that the electric fields typical of strongly electrified clouds substantially enhance the efficiency of droplet collisions. In contrast, the electric fields typical of fair-weather conditions have a negligible influence on the dynamics of droplet collisions.