Collisions of micron-sized, charged water droplets in still air

TL;DR

This study examines how electrical charges influence collisions of micron-sized water droplets in still air, combining theoretical analysis of dynamics with experimental validation to understand collision behavior.

Contribution

It introduces a theoretical framework analyzing charged droplet collisions, validated by experiments, highlighting the role of electrostatic forces and hydrodynamic interactions.

Findings

Stable manifolds determine collision outcomes.

Theoretical predictions match experimental results.

Electrostatic forces significantly affect droplet collision dynamics.

Abstract

We investigate the effect of electrical charge on collisions of hydrodynamically interacting, micron-sized water droplets settling through quiescent air. The relative dynamics of charged droplets is determined by hydrodynamic interactions, particle and fluid inertia, and electrostatic forces. We analyse the resulting relative dynamics of oppositely charged droplets by determining its fixed points and their stable and unstable manifolds. The stable manifold of a saddle point forms a separatrix that separates colliding trajectories from those that do not collide. The qualitative conclusions from this theory are in excellent agreement with experiments.