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PI (s) Info: Name Address Telephone E-mail

Project Title. University / Lab Logos. PI (s) Info: Name Address Telephone E-mail. PHOTO. Objectives and Navy Relevance:. Project Accomplishments and Plans. Noise from Ventilated Supercavities. Theoretical Modeling. Sphere dimensions chosen to match cavity

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PI (s) Info: Name Address Telephone E-mail

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  1. Project Title University / Lab Logos PI (s) Info: Name Address Telephone E-mail PHOTO Objectives and Navy Relevance: Project Accomplishments and Plans

  2. Noise from Ventilated Supercavities Theoretical Modeling • Sphere dimensions chosen to match cavity • volume in ARL Penn State experiments • Calculated lowest order resonance frequency of • spherical cavity – 57 Hz • Calculated characteristic dissipation time • constant of resonance due to gas exhausting • from end of cavity into main flow – 27 msec • Calculated directivity of sound in water • - kw = acoustic wavenumber in water • - r0 = sphere radius • Lowest order resonance is an omni- • directional monopole • Frequency of 6, 60 and 600 kHz corresponds to • figure (right) for kwr0 = 1, 10 and 100 • - Jet radiates directly as a beam for kwr0 > 100 The Axisymmetric Jet Simulates the Ventilation Gas Inflow Jet Impinging on the Cavity Wall Directivity of Sound Into Water

  3. Noise from Ventilated Supercavities Interface Vibration Measurements • Issues encountered while attempting to perform first • reported measurements of ventilated supercavity • interface vibrations include • - Low optical return from interface • - Reflections from nearby window and model surfaces • - Noise from LDV demodulation electronics and speckle • While it is possible to use LDVs in water tunnel • - Difficult to determine individual surfaces’ contributions to • overall measured spectral levels and distinguish velocity • data from noise • Comparison of the spectra measured with three LDVs • suggests that at least two of the spectra measured • thus-far may contain substantial contributions from • ventilated supercavity • Intend to employ 2 point correlation and beam • expansion techniques to discriminate and magnify, • respectively, the return contribution from the cavity • from the overall vibrometer return signal

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