ACOUSTO-FLUIDIC NOISE GENERATORS FOR AIRCRAFT COMPONENT STRUCTURE TESTING

HIGH INTENSITY ACOUSTIC NOISE GENERATORS ARE REQUIRED BY NASA TO IRRADIATE ADVANCED AIRCRAFT COMPONENT STRUCTURES ANDMATERIALS AT ELEVATED TEMPERATURES AND NOISE LEVELS UP TO 190 DB. PRESENTLY THE NOISE GENERATORS USED BY NASA AT THEIR LANGLEY ACOUSTIC RESEARCH FACILITY OPERATE AT LOW TEMPERATURES (70 DEGREES FAHRENHEIT) AT NOISE LEVELS UP TO 168 DB. CURRENTLY THESE GENERATORS ARE ELECTRO-MECHANICAL DEVICES WHICH MODULATE AIR FLOW AT FLOW RATES UP TO 6 LBS PER SECOND AND 30 PSI. THE OBJECTIVE OF THIS PROPOSED EFFORT IS TO EXAMINE THE TECHNICAL FEASIBILITY OF USING FLUIDIC OSCILLATORS TO GENERATE BOTH NARROW BAND (CONSTANT FREQUENCY) AND BROAD BAND NOISE USING HIGH TEMPERATURE (1800 DEGREES FAHRENHEIT) PROPELLANT GAS FLOWS TO GENERATE NOISE IN THE 190 DB POWER RANGE. THE PRESENT STATE-OF-THE-ART IN FLUIDIC GENERATORS ARE MINIATURE DEVICES WHICH HAVE BEEN OPERATED AT VERY LOW PRESSURES AND FLOW RATES TO PRODUCE SOUND PRESSURE LEVELS OF APPROXIMATELY 130 DB. THIS PROPOSED EFFORT IS A SURVEY OF FLUIDIC OSCILLATORS AND VORTEX DEVICES FOR POSSIBLE USE AS A HOT GAS NOISE GENERATING SOURCE IN THE LANGLEY ACOUSTIC RESEARCH FACILITY.THE RESULTS OF THIS PHASE I INVESTIGATION WILL BE USED TO ASSESS THE FEASIBILITY OF SCALING UP THE OSCILLATOR DESIGN FOR USE WITH HIGH TEMPERATURE PROPELLANT GAS FLOWS AT POWER LEVELS TO 190 DB.