REAL-TIME SUBSONIC FLOW VECTOR MEASUREMENT

WE PROPOSE TO EMPLOY A NEW NON-INTRUSIVE OPTICAL TECHNIQUE TO MEASURE INSTANTANEOUS THREE DIMENSIONAL FLOW VECTORS IN LARGE SCALE SUBSONIC F ACILITIES WITH HIGH (BETTER THAN MACH .02) ACCURACY. THE METHOD UTILI ZED A PULSED LASER BEAM TO "WRITE" AN ARBITRARY PATTERN INTO ORDINARY AIR BY MEANS OF STIMULATED RAMAN VIBRATIONAL EXCITATION. AFTER SUITAB LE TIME DELAY, DURING WHICH TIME THE INDUCED PATTERN CONVECTS WITH THE FLOW, THE NEW POSITION IS DETERMINED BY INDUCED FLUORESCENCE FROM A S ECOND LASER BEAM. AN IMAGE OF THE DISPLACEMENT IS CAPTURED WITH A VID EO CAMERA. BY WRITING A GRID, OR SIMILAR PATTERN, SIMULTANEOUS VECTOR S FROM MULTIPLE SPATIAL LOCATIONS WITHIN THE FLOW FIELD CAN BE DETERMI NED. THE ACCURACY OF THE MEASUREMENT IS LIMITED ONLY BY THE ABILITY T O DETERMINE TIME AND DISPLACEMENT, AND CAN BE PERFORMED AT VECTOR UPDA TE RATES OF 30 HZ USING READILY AVAILABLE COMMERCIAL EQUIPMENT. THE M EASUREMENT CAN BE PERFORMED IN ANY FLOW CONTAINING OXYGEN. IN THIS EF FORT WE PROPOSE A DETAILED STUDY, INCLUDING APPROPRIATE LABORATORY PRO OF-OF-CONCEPT MEASUREMENTS, OF THE APPLICABILITY OF THE TECHNIQUE TO S UBSONIC FLOW. THE DEVELOPMENT OF AN INHERENTLY ACCURATE TIME-OF-FLIGH T METHOD, WITHOUT THE REQUIREMENT OF PARTICLE SEEDING, CONSTITUTES A U NIQUE NEW CAPABILITY FOR LARGE SCALE FACILITIES, WHERE SEEDING IS A DI FFICULT PROBLEM. THE RESULT OF THIS EFFORT WILL BE A DETAILED DESIGN OF A PROTOTYPE SYSTEM FOR IMPLEMENTATION IN AEDC FACILITIES.