Clustering and collision of inertial particles in random velocity fields

TL;DR

This paper investigates how clustering affects collision rates of inertial particles in turbulent-like flows, revealing that clustering reduces energetic collisions due to caustic formation, regardless of flow dimensionality.

Contribution

It provides a theoretical analysis linking clustering and collision rates, emphasizing the role of caustic formation in inertial particle dynamics.

Findings

Clustering decreases the likelihood of energetic collisions.

The effect is independent of flow dimensionality.

Caustic formation is key to collision dynamics.

Abstract

The influence of clustering on the collision rate of inertial particles in a smooth random velocity field, mimicking the smaller scales of a turbulent flow, is analyzed. For small values of the the ratio between the relaxation time of the particle velocity and the characteristic time of the field, the effect of clusters is to make more energetic collisions less likely. The result is independent of the flow dimensionality and is due only to the origin of collisions in the process of caustic formation.