Turbulent transport of material particles: An experimental study of finite size effects

TL;DR

This study experimentally investigates how finite-sized, neutrally buoyant particles behave in turbulent air flows, revealing that particle size influences acceleration variance but not the overall acceleration distribution shape.

Contribution

It introduces an acoustic Lagrangian tracking method combined with adjustable soap bubble particles to analyze finite size effects in turbulent transport.

Findings

Acceleration variance decreases with particle size.

Acceleration distribution shape remains largely unaffected by size.

Results align with classical pressure fluctuation scaling.

Abstract

We use an acoustic Lagrangian tracking technique, particularly adapted to measurements in open flows, and a versatile material particles generator (in the form of soap bubbles with adjustable size and density) to characterize Lagrangian statistics of finite sized, neutrally bouyant, particles transported in an isotropic turbulent flow of air. We vary the size of the particles in a range corresponding to turbulent inertial scales and explore how the turbulent forcing experienced by the particles depends on their size. We show that, while the global shape of the intermittent acceleration probability density function does not depend significantly on particle size, the acceleration variance of the particles decreases as they become larger in agreement with the classical scaling for the spectrum of Eulerian pressure fluctuations in the carrier flow.