Tracking the dynamics of translation and absolute orientation of a sphere in a turbulent flow

TL;DR

This study investigates the complex 6D motion of a large sphere in turbulent flow, revealing unexpected intermittency in its velocities and accelerations through a novel tracking algorithm.

Contribution

Introduces an efficient method for tracking the orientation of a sphere in turbulence and analyzes its dynamic behavior, highlighting surprising intermittency effects.

Findings

Intermittency observed in linear and angular velocities.

Novel algorithm effectively tracks sphere orientation.

Size of sphere comparable to turbulent integral scale.

Abstract

We study the 6-dimensional dynamics -- position and orientation -- of a large sphere advected by a turbulent flow. The movement of the sphere is recorded with 2 high-speed cameras. Its orientation is tracked using a novel, efficient algorithm; it is based on the identification of possible orientation `candidates' at each time step, with the dynamics later obtained from maximization of a likelihood function. Analysis of the resulting linear and angular velocities and accelerations reveal a surprising intermittency for an object whose size lies in the integral range, close to the integral scale of the underlying turbulent flow.