Particle growth in turbulent flow under dynamically critical Stokes conditions

TL;DR

This paper introduces a theory explaining how inertial particles grow in turbulent flows through dynamic clustering at scales larger than the Kolmogorov length, predicting a limiting size based on flow properties.

Contribution

The paper presents a novel model linking particle growth to a dynamically critical Stokes number, incorporating flow scale evolution during particle aggregation.

Findings

Predicts particle size limit based on inertial range extent

Describes growth mechanism involving orbiting vortices

Provides a framework for geophysical multi-phase flows

Abstract

A simple theory, based on observations of snowflake distribution in a turbulent flow, is proposed to model the growth of inertial particles as a result of dynamic clustering at scales larger than the Kolmogorov length scale. Particles able to stick or coalesce are expected to grow in size in flow regions where preferential concentration is predicted by a critical Stokes number $St=\tau_p/\tau_f \simeq 1 $. We postulate that, during growth, $St$ remains critical, with the particle response time $\tau_p$ evolving according to the specific flow time scale $\tau_f$ defined by the vortices around which progressively larger particles end up orbiting. This mechanism leads to the prediction of the limiting size of aggregating particles in a turbulent flow. Such limit is determined by the extent of the turbulent inertial range, which can be formulated as a function of accessible integral-scale quantities. The proposed dynamically critical Stokes growth provides a framework to interpret particle aggregation, size growth and particle cluster growth in various geophysical multi-phase flows.