Rotation Rate of Particle Pairs in Homogeneous Isotropic Turbulence

TL;DR

This study investigates the rotation dynamics of particle pairs in homogeneous isotropic turbulence at high Reynolds number, revealing limitations of classical models and proposing a multifractal approach to better capture intermittent behaviors.

Contribution

The paper introduces a multifractal formalism to accurately model the PDFs of particle pair rotation rates, accounting for intermittency neglected by Kolmogorov scaling.

Findings

Kolmogorov scaling fails to predict PDFs accurately

Multifractal formalism captures intermittent rotation events

PDFs show stretched tails and high kurtosis at small separations

Abstract

Understanding the dynamics of particles in turbulent flow is important in many environmental and industrial applications. In this paper, the statistics of particle pair orientation is numerically studied in homogeneous isotropic turbulent flow, with Taylor microscale Reynolds number of 300. It is shown that the Kolmogorov scaling fails to predict the observed probability density functions (PDFs) of the pair rotation rate and the higher order moments accurately. Therefore, a multifractal formalism is derived in order to include the intermittent behavior that is neglected in the Kolmogorov picture. The PDFs of finding the pairs at a given angular velocity for small relative separations reveals extreme events with stretched tails and high kurtosis values. Additionally, The PDFs are found to be less intermittent and follow a complementary error function distribution for larger separations.