Direct Measurement of Turbulent Shear

TL;DR

This paper introduces a photon correlation method for measuring shear rate components in turbulent flows, providing results comparable to Laser Doppler velocimetry but with reduced noise, and enabling detailed statistical analysis.

Contribution

The paper presents a novel photon correlation technique for shear measurement that is applicable to both two-dimensional and three-dimensional turbulent flows, with improved noise performance.

Findings

Method yields shear rate mean and standard deviation.

Results match Laser Doppler velocimetry measurements.

Provides a simple transform of shear rate probability density.

Abstract

A photon correlation method is introduced for measuring components of the shear rate tensor in a turbulent soap film. This new scheme, which is also applicable to three-dimensional flows, is shown to give the same results as Laser Doppler velocimetry, but with less statistical noise. The technique yields the mean shear rate s, its standard deviation, and a simple mathematical transform of the probability density function P(s) of the shear rate itself.