Project Title:

Remote Characterization of Wind-Tunnel Turbulence

08.20-9030
Remote Characterization of Wind-Tunnel
	Turbulence
Physical Sciences, Inc.
Research Park
PO Box 3100
Andover, MA 01810
Lawrence G. Piper  (617-475-9030)
LaRC -- NAS1-18617

Abstract:

	 An innovative monitor for density fluctuations in the boundary layer of turbulent
flows around test objects in wind tunnels is the subject of this project. It is based
upon the laser-induced fluorescence from molecular oxygen which is excited when 193
nm light from an argon-fluoride excimer laser propagates through the air. Partial
pre-dissociation gives the excited molecular oxygen a very short lifetime and, therefore,
renders it immune to electronic quenching. In consequence, the intensity of the observed
laser-induced fluorescence is directly proportional to the local number density of
the volume being probed. Detecting this fluorescence with a two-dimensional diode
array as the laser beam scans above the surface of the test object maps out the turbulence
in two dimensions. Three-dimensional mapping results from repeating the laser scans
at a number of distances above the surface of the test object.
	The Phase I program used an available, lower power laser to investigate the properties
of room-temperature oxygen fluorescence. Laser-excitation scans of several absorption
bands were detected in fluorescence, and the results used to demonstrate a potential
extension of the technique to simultaneous temperature measurements. A preliminary
imaging experiment was conducted in order to validate a computer model of the fluorescence
yield.

Potential Commercial Application:

Potential Commercial Application: Applications would be in government research laboratories,
aerospace industries, automotive industries, universities, and other organizations
conducting gas-dynamic experiments.