Author

R. J. Adrian

Abstract

The design and performance of a laser Doppler velocimeter (LDV) used in a turbulent water-overice convection experiment are described. The LDV was operated in a reference beam mode with an ultrasonic diffraction grating shifting the reference beam frequency to provide bipolar sensing of the vertical velocity, and a phase-locked loop was used to demodulate the Doppler frequency information. The maximum observed velocities in the experiment were ± 1 mm/sec, and the accuracy of instantaneous measurement was limited by Brownian motion and laser line width to ± .04 mm/sec for a 2 Hz frequency response. The practical difficulties encountered in this system are discussed, and typical results are presented. In particular, it was found that when the photocurrent signal-to-noise ratio was low, the relation between the velocity and the frequency demodulated output exhibited a severe loss in sensitivity. An analysis of this effect is given for LDV systems utilizing high scattering particle concentrations, from which an equation relating the sensitivity loss to the signal-to-noise ratio is derived.

Meeting Name

3rd Biennial Symposium on Turbulence in Liquids (1973: Sep., Rolla, MO)

Department(s)

Chemical and Biochemical Engineering

Document Type

Article - Conference proceedings

Presentation Type

Contributed Paper

Session

Laser-Doppler Velocimetry

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 1973 University of Missouri--Rolla, All rights reserved.

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