BOUNDARY LAYER FLOW NOISE

THE PERFORMANCE OF MANY ADVANCED UNDERWATER ACOUSTIC SENSOR SYSTEMS IS LIMITED BY UNWANTED NOISE CAUSED BY THE TURBULENT BOUNDARY LAYER (TBL). THE TBL MAY ALSO EXCITE UNWANTED NOISE AND VIBRATION (FLOW NOISE) IN A VARIETY OF MARINE AND AIRCRAFT VEHICLES. A SIGNIFICANT AMOUNT OF FLOW NOISE REDUCTION HAS BEEN REPORTED WHEN ANISOTROPIC COMPLIANT WALLS HAVE BEEN TESTED. THE PROPOSED WORK IS TO DEVELOP THE TOOLS NECESSARY TO CALCULATE AND MEASURE THE WAVEVECTOR-FREQUENCY SPECTRA (INCLUDING THE LOW-WAVENUMBER REGION) OF TBL WALL PRESSURE FLUCTUATIONS ON ANISOTROPIC COMPLAINT LAYERS. A TECHNIQUE FOR DETERMINING THE PROPERTIES OF THE COMPLIANT LAYERS WILL BE INCLUDED AS PART OF THE MEASUREMENT SYSTEM. A POSSIBLE DESIGN OF THE MEASUREMENT APPARATUS WILL BE AN EXTENSION OF AN ACOUSTIC SENSOR SYSTEM WHICH IS CURRENTLY UNDER DEVELOPMENT AT ATLANTIC APPLIED RESEARCH CORPORATION. THE APPARATUS WILL USE THE COMPLAINT LAYER AS AN INTEGRAL PART OF ITS DESIGN. THE DESIGN GOAL WILL INCLUDE THE ABILITY TO USE A WIDE VARIETY OF COMPLIANT MATERIALS (ISOTROPIC OR ANISOTROPIC), AND A WAVENUMBER RANGE AND RESOLUTION SURPASSING MEASURMENT SYSTEMS CURRENTLY AVAILABLE. THEORETICAL EFFORTS WILL BE CONCENTRATED ON EVALUATING EXPERIMENTAL RESULTS AND GUIDING EXPERIMENTAL TESTS AS WELL AS INVESTIGATING THE EFFECTS OF THE COMPLAINT LAYER ON THE TBL SPECTRUM.