Dynamical regimes and clustering of small neutrally buoyant inertial particles in stably stratified turbulence

TL;DR

This paper investigates the behavior of small neutrally buoyant inertial particles in stably stratified turbulence, revealing their clustering tendencies and different regimes based on particle and flow parameters through simulations.

Contribution

It introduces a detailed analysis of inertial particle dynamics in stratified flows using the Maxey-Riley framework and identifies distinct regimes and clustering behaviors.

Findings

Particles behave as forced damped oscillators depending on parameters.

Small neutrally buoyant particles tend to cluster in low vorticity regions.

Particles exhibit fundamentally different behavior than tracers.

Abstract

Inertial particles in stably stratified flows play a fundamental role in geophysics, from the dynamics of nutrients in the ocean to the dispersion of pollutants in the atmosphere. We consider the Maxey-Riley equation for small neutrally buoyant inertial particles in the Boussinesq approximation, and discuss its limits of validity. We show that particles behave as forced damped oscillators, with different regimes depending on the particles Stokes number and the fluid Brunt-V\"ais\"al\"a frequency. Using direct numerical simulations we study the particles dynamics and we show that small neutrally buoyant particles in these flows tend to cluster in regions of low local vorticity. The particles, albeit small, behave fundamentally differently than tracers.