STIMULATED BRILLOUIN DIAGNOSTICS OF HYPERSONIC FLOWS

THE DEVELOPMENT OF VEHICLES SUCH AS THE NATIONAL AEROSPACE PLANE REQUIRES A KNOWLEDGE OF THE THERMODYNAMICS OF THE AIR FLOW AT HYPERSONIC SPEEDS. THE CONVENTIONAL LASER DOPPLER VELOCIMETRY TECHNIQUE IS INCAPABLE OF SUPPLYING INFORMATION AT THE REQUIRED LEVEL OF DETAIL BECAUSE THE MEASURED DUST PARTICLES NO LONGER FOLLOW THE FLOW LINES AT HIGH VELOCITIES. OUR OBJECTIVE IS TO MEASURE THE MOTION OF THE FLOWING MOLECULES USING A WELL KNOWN SPECTROSCOPIC TECHNIQUE, STIMULATED BRILLOUIN SCATTERING (SBS). THIS APPROACH WOULD WORK WELL AT ALL SPEEDS, HAS THE ADVANTAGE OF A HIGH SIGNAL - TO - NOISE RATIO, AND WILL PERMIT MEASUREMENTS TO BE MADE FROM WITH AN IN-FLIGHT VEHICLE DUE TO THE BACKSCATTERING GEOMETRY. WE PLAN TO INVESTIGATE THE FLOW PARAMETER RANGE OVER WHICH SBS IS APPLICABLE, AND TO DESIGN A PROTOTYPE SYSTEM WHICH IN THE PHASE II PROGRAM WILL ENABLE US TO VERIFY THE PREDICTED PERFORMANCE IN A LABORATORY SCALE WIND TUNNEL.