On the clustering of finite-size particles in turbulence

TL;DR

This study experimentally examines how finite-size particles of different densities distribute in turbulent flows, revealing that only heavy particles cluster while neutrally buoyant particles distribute evenly, challenging the sole reliance on Stokes number for modeling.

Contribution

It demonstrates that particle density and finite size influence clustering behavior, showing Stokes number alone is insufficient for predicting particle distribution in turbulence.

Findings

Neutrally buoyant particles distribute homogeneously.

Heavy particles tend to cluster in turbulence.

Stokes number is not the only key parameter for particle distribution.

Abstract

We investigate experimentally the spatial distributions of heavy and neutrally buoyant particles of finite size in a fully turbulent flow. As their Stokes number (i.e. ratio of the particle viscous relaxation time to a typical flow time scale) is close to 1, one may expect both classes of particles to aggregate in specific flow regions. This is not observed. Using a Voronoi analysis we show that neutrally buoyant particles sample turbulence homogeneously, whereas heavy particles do cluster. One implication for the understanding and modeling of particle laden flows, is that the Stokes number cannot be the sole key parameter as soon as the dynamics of finite-size objects is considered.