Coagulation and fragmentation dynamics of inertial particles

TL;DR

This paper investigates how inertial particles in oscillating flows undergo coagulation and fragmentation, reaching a steady state where size distribution depends mainly on fragmentation mechanisms rather than coagulation rates.

Contribution

It demonstrates that in time-periodic flows, the steady-state particle size distribution is primarily influenced by fragmentation, with coagulation affecting only transient dynamics.

Findings

Steady state size distribution is largely independent of coagulation process.

Fragmentation mechanism determines the steady state.

Flow variations with similar shear forces produce similar size distributions.

Abstract

Inertial particles suspended in many natural and industrial flows undergo coagulation upon collisions and fragmentation if their size becomes too large or if they experience large shear. Here we study this coagulation-fragmentation process in time-periodic incompressible flows. We find that this process approaches an asymptotic, dynamical steady state where the average number of particles of each size is roughly constant. We compare the steady-state size distributions corresponding to two fragmentation mechanisms and for different flows and find that the steady state is mostly independent of the coagulation process. While collision rates determine the transient behavior, fragmentation determines the steady state. For example, for fragmentation due to shear, flows that have very different local particle concentrations can result in similar particle size distributions if the temporal or spatial variation of shear forces is similar.