Accession Number:

ADA238857

Title:

Three-Dimensional Rapidly Scanning Laser Doppler Velocimeter with Low SNR Signal Processing

Descriptive Note:

Final rept. 1 Feb 88-30 Nov 90,

Corporate Author:

VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF AEROSPACE AND OCEAN ENGINEERING

Report Date:

1990-11-30

Pagination or Media Count:

74.0

Abstract:

A rapidly scanning directionally sensitive three-velocity-component laser Doppler velocimeter RSLDV has been designed. It permits rapid scans through three-dimensional flows to obtain space-time velocity information and almost instantaneous velocity profiles vital to understanding such flows. A flexible optical system allows for easy variation of the fringe spacing as well as the location and size of the measurement volume. Several optical techniques to maintain coincidence between the horizontal, U and W, and vertical, V, probe volumes were investigated. A lens, used like a prism, and two plane mirrors for the out of plane scanning laser beam maintains good coincidence between the probe volumes, while maintaining some flexibility. Moving fringe patterns in the horizontal and vertical planes are produced by a dual water Bragg cell. The Doppler frequency is independent of the position of the receiving optics, and only one photomultiplier tube PMT is needed to receive the signals for all three velocity components.

Subject Categories:

  • Meteorology
  • Test Facilities, Equipment and Methods
  • Active and Passive Radar Detection and Equipment
  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE