PROBE FOR FLUCTUATING TEMPERATURE MEASUREMENTS IN TURBULENT SUPERSONIC FLOWS

AN INNOVATIVE COHERENT OPTICAL MEASUREMENT METHOD TO DIAGNOSE HIGH FREQUENCY FLUCTUATING COMPONENTS IN A HIGH MACH NUMBER FLOW IS PROPOSED. THE SPECIES CONCENTRATION, STATIC AND STAGNATION TEMPERATURE OF THE GAS MIXTURE, WILL BE MEASURED DIRECTLY AND SIMULTANEOUSLY DURING A SINGLE LASER PULSE, DURING ABOUT 10 NSEC. THIS MAKES THE MEASUREMENT COMPATIBLE WITH HIGH FREQUENCY TURBULENT REGIMES. THE PRESSURE (STATIC AND STAGNATION) AS WELL AS THE VELOCITY WILL BE DETERMINED BY THE MEASURED DATA. OTHER ATTRACTIVE AND UNIQUE PROPERTIES OF THE PROPOSED APPARATUS INCLUDE A SPATIAL RESOLUTION OF ABOUT 10 MICRONS, AND A MEASUREMENT SENSITIVITY EQUIVALENT TO A PARTIAL PRESSURE OF LESS THAN 1 MILLITORR OF MOLECULAR NITROGEN. THE PROPOSED SYSTEM OPERATES BY A NOVEL COHERENT SCATTERING METHOD, THAT PROVIDES CONSIDERABLE ADVANTAGES OVER EXISTING SCATTERING TECHNIQUES. THE MULTIPLE MEASUREMENT USING A SINGLE APPARATUS IS POSIBLE DUE TO THE TUNABILITY OF THE COHERENT SOURCE AS WELL AS THE CONVOLUTED INFORMATION OBTAINED IN THE OUTPUT SIGNAL. THE PROPOSED LABORATORY SETUP WILL INCLUDE A NOVEL SINGLE LASER INVENTED BY THE PRINCIPAL INVESTIGATOR, SO THAT NO ADDITIONAL COHERENT RADIATION SOURCES ARE NECESSARY.