Direct measurement of turbulent shear

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 σ , and a simple mathematical transform of the probability density function P ( s ) of the shear rate itself.