Abstract

Homodyne Correlation Spectroscopy (HCS) is a very useful technique for studying the flow characteristics of fluid turbulence where the intensity of the laser light scattered from small seeded particles is detected and processed in the time domain by means of fast digital correlators. The intensity auto correlation function g(τ) of the scattered light measured by these correlators is sensitive to the relative velocity fluctuations V(R,t) between pairs of seed particles in the flow separated by a distance R thereby characterizing the spatial characteristics of the flow. It has been shown both numerically and experimentally that turbulent flow is intermittent in nature [1], The intermittent effects are characterized by increasingly non-Gaussian statistics of velocity differences or velocity gradients in the flow for smaller and smaller scales of turbulence. It is predicted that the deviation from gaussian statistics is due to the presence of small scale coherent structures [1] and inactive regions [2] in the turbulent flow field. We have recently [3] employed the HCS technique to experimentally verify our theoretical model for the probability distribution function P(V(R,t)) of relative velocity fluctuations V(R,t) and the present work highlights some of our results in the light of above predictions regarding the intermittent nature of turbulence.

© 1996 Optical Society of America