ADVANCED DEVELOPMENT OF THREE-COMPONENT LASER DOPPLER VELOCIMETRY

IN THE PROPOSED EFFORT, SIMULTANEOUS PARTICLE SIZING CAPABILITY WILL BE ADDED TO A TWO-COMPONENT LASER DOPPLER VELOCIMETER TO FORM A THREE-COMPONENT SYSTEM. THIS COMBINATION OF CAPABILITIES WILL PRODUCE AN INSTRUMENT UNIQUELY SUITED TO THE CHARACTERIZATION OF HIGH SPEED, TURBULENT, THREE-DIMENSIONAL FLOW FIELDS SUCH AS ENCOUNTERED IN HELICOPTER ROTOR FLOWS. THE RECENTLY DEVELOPED PHASE DOPPLER PARTICLE ANALYZER (PDPA), TO BE USED IN THIS EFFORT, CAN PROVIDE SIMULTANEOUS PARTICLE SIZE INFORMATION WHICH, WHEN USED IN CONJUNCTION WITH VELOCITY DATA FROM INDIVIDUAL PARTICLES, CAN EVALUATE THE RESPONSE OF PARTICLES NEEDED TO SEED THE AIRFLOW FOR THE LDV MEASUREMENTS. AN IMPROVED METHOD FOR SIGNAL COINCIDENCE IS PROPOSED AND WILL BE INCORPORATED INTO THE SYSTEM. THIS WILL INSURE SIMULTANEITY OF THE THREE VELOCITY MEASUREMENTS AS WELL AS THE PARTICLE SIZE MEASUREMENT. TOTAL INSTANTANEOUS VELOCITIES CAN BE DETERMINED ALONG WITH REYNOLD'S SHEAR STRESS FOR THE FLUID. TIME-TAGGING OF INDIVIDUAL EVENTS DURING DATA ACQUISITION WILL PERMIT TEMPORAL CORRELATIONS AND ANALYSIS OF UNSTEADY PHENOMENA.