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Whole-Field Measurements in Gas-Phase Turbulent Flows

Dimotakis, Paul E. and Fourguette, Dominique (1995) Whole-Field Measurements in Gas-Phase Turbulent Flows. California Institute of Technology , Pasadena, CA. (Unpublished)

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The purpose of this experimental, nine-month effort was to investigate the scalar field in fully-developed, gas-phase, turbulent flows, using planar index-of-refraction imaging at elevated pressures (p ≃ 10 atm). The motivation behind this work is to further our understanding of phenomena that rely on the behavior of scalar gradients, such as aero-optic effects, laser propagation through, and scattering by, gas-phase turbulent flows, as well as turbulent mixing and combustion. In this effort, we have used planar laser-Rayleigh scattering to image simultaneously the index-of-refraction field of a turbulent jet and the optical degradation of the planar laser probe beam caused by the turbulent flow-field. From these results, we have demonstrated that conducting these experiments at elevated pressure increases the index-of-refraction gradients and improves the signal-to-noise ratio over measurements conducted at atmospheric conditions. The optical degradation occurs in the jet-fluid region and manifests itself as a spatial amplitude modulation (streaks) in the laser sheet. This optical degradation illustrates the same loss of coherence undergone by laser beams and by coherent information when propagating through the turbulent atmosphere.

Item Type:Report or Paper (Technical Report)
Additional Information:© 1995 California Institute of Technology. Air Force Office of Scientific Research Grant No. F49620-94-1-0283 Annual Technical Report: Period ending 14 February 1995.
Group:Graduate Aeronautical Laboratories (Fluid Mechanics), GALCIT
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)F49620-94-1-0283
Subject Keywords:aero-optics, index-of-refraction, optical degradation, turbulence
Record Number:CaltechAUTHORS:20141104-110123516
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51232
Deposited On:04 Nov 2014 21:49
Last Modified:17 Nov 2021 17:35

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