Experimental Lagrangian structure functions in turbulence

TL;DR

This paper presents experimental measurements of Lagrangian structure functions in turbulence, highlighting the importance of accurate sampling and volume effects, and discusses intermittency and multifractal modeling at intermediate Reynolds numbers.

Contribution

It introduces a robust method to address measurement volume bias in Lagrangian turbulence experiments and provides new insights into intermittency at small scales.

Findings

Strong intermittency observed at dissipation scales

Measurement volume bias can significantly affect results

Multifractal model partially explains the observed intermittency

Abstract

Lagrangian properties obtained from a Particle Tracking Velocimetry experiment in a turbulent flow at intermediate Reynolds number are presented. Accurate sampling of particle trajectories is essential in order to obtain the Lagrangian structure functions and to measure intermittency at small temporal scales. The finiteness of the measurement volume can bias the results significantly. We present a robust way to overcome this obstacle. Despite no fully developed inertial range we observe strong intermittency at the scale of dissipation. The multifractal model is only partially able to reproduce the results.