A Scanning laser-velocimeter technique for measuring two-dimensional wake-vortex velocity distributions
Abstract
A rapid scanning two dimensional laser velocimeter (LV) has been used to measure simultaneously the vortex vertical and axial velocity distributions in the Langley Vortex Research Facility. This system utilized a two dimensional Bragg cell for removing flow direction ambiguity by translating the optical frequency for each velocity component, which was separated by band-pass filters. A rotational scan mechanism provided an incremental rapid scan to compensate for the large displacement of the vortex with time. The data were processed with a digital counter and an on-line minicomputer. Vaporized kerosene (0.5 micron to 5 micron particle sizes) was used for flow visualization and LV scattering centers. The overall measured mean-velocity uncertainity is less than 2 percent. These measurements were obtained from ensemble averaging of individual realizations.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- May 1980
- Bibcode:
- 1980STIN...8024594G
- Keywords:
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- Aircraft Wakes;
- Laser Doppler Velocimeters;
- Scanners;
- Velocity Measurement;
- Vortices;
- Wind Tunnel Tests;
- Axial Flow;
- Bandpass Filters;
- Bragg Cells;
- Flow Visualization;
- Particle Size Distribution;
- Vertical Distribution;
- Instrumentation and Photography