WIND TUNNEL NOISE REDUCTION

SOUND AND TURBULENCE GENERATED BY THE INTERACTION BETWEEN THE FLOW AND STRUCTURES IN WIND TUNNELS ADDS TO THE FAN NOISE AND ESTABLISHES THE LOWER LIMIT OF BACKGROUND NOISE. IT INTERFACES WITH THE MEASUREMENT OF ACOUSTIC RADIATION FROM TEST ARTICLES AND THE PERFORMANCE OF TRANSITION EXPERIMENTS. RATHER THAN ATTENUATING SOUND AFTER IT HAS BEEN GENERATED, THIS PROJECT ADDRESSES THE REDUCTION OF FLOW-STRUCTURE NOISE AT THE SOURCE BY MODIFICATION OF STRUCTURES SUCH AS TURNING VANES, STRUTS, AND NOZZLE LIPS. THE CONCEPT INVOLVES THE USE OF POROUS, PERFORATED, OR SERRATED EDGES TO PROVIDE A GRADUAL HYDRODYNAMIC AND ACOUSTIC TRANSITION AT THE EDGE SO THAT THE FLOW EXPERIENCESA GRADUAL CHANGE OF BOUNDARY CONDITIONS FROM A SOLID BODY TOFREE AIR RATHER THAN A DISCONTINUOUS CHANGE AT A LEADING OR TRAILING EDGE. EXPERIMENTS ON THREE TYPES OF TRAILING EDGESWILL BE PERFORMED IN THE FIRM'S QUIET WIND TUNNEL TO VALIDATE THE ANALYTICAL RELATIONS AND TO ESTABLISH SCALING RELATIONS. RESULTS WILL BE APPLICABLE TO THE RETROFIT OF EXISTING FACILITIES AND TO THE DESIGN OF NEW ACOUSTIC RESEARCH TUNNELS. RESULTS WILL HAVE APPLICATION TO MANY GOVERNMENT, AEROSPACE,AND AUTOMOBILE INDUSTRY WIND TUNNELS. QUIET WIND TUNNELS ARE PLANNED IN ALL THESE AREAS.