Flow structures govern particle collisions in turbulence

TL;DR

This paper investigates how different flow structures in turbulence influence particle collision rates, revealing that straining zones and vortex-strain interactions significantly affect collision dynamics and aggregate formation.

Contribution

It quantifies the correlation between turbulence structures and particle collisions, highlighting the roles of straining zones and vortex-strain worm-rolls in natural aggregation processes.

Findings

Straining zones mainly cause rapid head-on collisions.

Vortex-strain worm-rolls are crucial for particle aggregation.

Flow structures significantly influence collision rates.

Abstract

The role of the spatial structure of a turbulent flow in enhancing particle collision rates in suspensions is an open question. We show and quantify, as a function of particle inertia, the correlation between the multiscale structures of turbulence and particle collisions: Straining zones contribute predominantly to rapid head-on collisions compared to vortical regions. We also discover the importance of vortex-strain worm-rolls, which goes beyond ideas of preferential concentration and may explain the rapid growth of aggregates in natural processes, such as the initiation of rain in warm clouds.