Collision rates of charged aerosol particles in a linear flow*

Micron-sized charged spheres suspended in air have significance in cloud microphysical processes and influence the droplet size distribution in the cloud. This work studies the collision rate of like-charged dielectric spheres in a linear flow. Depending on the relative size, charges, and separation of the spheres, the electrostatic interaction force between them can be attractive, zero, or repulsive. We calculate the collision rate as a function of the electrostatic force relative to the flow for a range of values of size ratio, charge ratio. We find that polydispersity in terms of particle sizes and charges significantly influences the collision rates. For a charge and size ratio combination for which the near field electrostatics is repulsive, collision is possible below a critical value at which the background flow is strong enough to overcome the electrostatic force. As the electrostatic force increases from zero, we observe two different types of dynamics depending on the size and charge ratio values. In one case, the collision efficiency increases to a maximum and then decreases to zero. In the other case, the collision efficiency decreases monotonically to zero.