AEROACOUSTIC ANALYSIS OF ROTOR/ROTOR WAKE INTERACTIONS

THE IMPORTANCE OF REDUCING THE NOISE EMITTED BY HELICOPTER ROTORS HAS BEEN WIDELY RECOGNIZED FOR MANY YEARS. PREVIOUS WORK BY CONTINUUM DYNAMICS IN THE ANALYSIS OF ROTOR AEROACOUSTICS LED TO THE DEVELOPMENT OF AN EFFICIENT AND ACCURATE LAGRANGIAN SIMULATION OF THE UNSTEADY VORTICITY FIELD IN THE VICINITY OF HELICOPTER MAIN ROTOR THAT COULD SERVE AS THE FOUNDATION FOR A GENERAL ANALYSIS OF THE NOISE GENERATED BY MAIN-ROTOR-WAKE/TAIL-ROTOR INTERACTIONS. THE MAIN-ROTOR/TAIL-ROTOR SIMULATION DEVELOPED PREVIOUSLY, THOUGH, WAS DESIGNED AS A TECHNOLOGY DEMONSTRATION FOR APPLICATION TO A LIMITED CLASS OF INTERACTIONS; WHILE THE RESULTS TO DATE HAVE BEEN QUITE PROMISING, THE CURRENT CAPABILITIES OF THE ANALYSIS MUST BE CONSIDERABLY ENHANCED BEFORE IT CAN BECOME A GENERALLY APPLICABLE TOOL FOR THE PREDICTION OF HELICOPTER ROTOR NOISE. THE OVERALL OBJECTIVE OF THE EFFORT PROPOSED HERE IS TO DEMONSTRATE TECHNIQUES FOR GENERALIZING THE EXISTING ANALYSIS SO IT CAN ADDRESS BROAD CLASSES OF ROTOR-WAKE/ROTOR INTERACTION PHENOMENA, PARTICULARLY THOSE THAT FIGURE IN MAIN ROTOR NOISE GENERATION. THE PRESENT PROPOSAL PRESENTS THE DETAILSOF THESE ENHANCEMENTS, WHICH FOCUS ON THE EXPANSION OF THE RECONSTRUCTION PROGRAM DEVELOPED IN THE PREVIOUS EFFORT TO HANDLE ARBITRARY VORTEX WAKE INTERSECTIONS OF THREE-DIMENSIONAL REGIONS AROUND OR NEAR MAIN ROTORS, THE DEVELOPMENT OF NEW NEARFIELD VELOCITY CORRECTIONS FOR SUCH INTERACTIONS, AND PRELIMINARY STUDY OF METHODS FOR USING THE NEW HIGH-RESOLUTION FLOW FIELD ANALYSIS FOR ACOUSTIC PREDICTIONS.