AN ASSESSMENT OF LASER VELOCIMETER POTENTIAL IN HYPERSONIC FLOWS

AT PRESENT, PROGRESS IN COMPUTATIONAL FLUID DYNAMICS OF HIGHSPEED FLOWS IS RESTRICTED BY THE NEED FOR EXPERIMENTAL DATA WHICH CAN BE USED FOR THE DEVELOPMENT OF EMPIRICAL TURBULENCE MODELS AND TO VALIDATE NAVIER-STOKES CODES. ALTHOUGH SOME HOT WIRE DATA HAVE BEEN OBTAINED IN PREVIOUS YEARS, THEY ARE OF QUESTIONABLE RELIABILITY DUE TO THE ASSUMPTIONS WHICH MUST BE MADE TO DETERMINE VELOCITY FLUCTUATION LEVELS FROM THE MEASURED HOT WIRE VARIABLES. HOWEVER, THE ADVENT OF THE LASER VELOCIMETER ALLOWS US TO MEASURE VELOCITY FLUCTUATIONS DIRECTLY, IN A LINEAR, NON-INTRUSIVE MANNER OF PARTICULAR VALUE IS THE CAPABILITY TO MEASURE THE TURBULENT SHEAR STRESSES WHICH IS AN IMPRACTICAL TASK WITH HOT WIRES. HOWEVER, BEFORE COMPLEX AND EXPENSIVE TEST PLANS ARE MADE, AN ASSESSMENT OF THE POTENTIAL FOR LASER VELOCIMETRY IN HYPERSONIC FLOWS MUST BE MADE. THE PURPOSE OF THIS PROPOSAL IS TO MAKE SUCH A DETERMINATION FOR FLOWFIELD MEASUREMENTS IN THE NASA AMES 3.5 FT. HYPERSONIC WIND TUNNEL.