Geotropic tracers in turbulent flows: a proxy for fluid acceleration

TL;DR

This paper introduces a novel method using geotropic tracers to measure fluid acceleration in turbulent flows, supported by simulations that validate the relation between tracer orientation and acceleration statistics.

Contribution

It proposes a new experimental technique for local acceleration measurement in turbulence using the orientation of neutrally buoyant, displaced-center spherical tracers.

Findings

The orientation of tracers correlates linearly with acceleration components.

Simulations confirm the method can reconstruct acceleration statistics.

The approach is feasible for experimental turbulence studies.

Abstract

We investigate the statistics of orientation of small, neutrally buoyant, spherical tracers whose center of mass is displaced from the geometrical center. If appropriate-sized particles are considered, a linear relation can be derived between the horizontal components of the orientation vector and the same components of acceleration. Direct numerical simulations are carried out, showing that such relation can be used to reconstruct the statistics of acceleration fluctuations up to the order of the gravitational acceleration. Based on such results, we suggest a novel method for the local experimental measurement of accelerations in turbulent flows.