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Acoustic Tomography of Natural Bubble Fields and Ship Wakes

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The primary long-range objectives are the development and the refinement of algorithms for acoustic tomography with applications to quantitative measurement of bubble fields. Natural bubble fields from breaking waves in littoral regions have a profound effect on performance of sonar systems while the wakes of ships have a debilitating impact on the effectiveness of anti-torpedo torpedo defense systems. This research investigates the feasibility of using acoustic tomography as a suitable method to determine physical properties of bubble fields e.g., attenuation and bubble size distribution. The current research s scientific objectives seek to establish methods to determine physical properties of bubbly water from in situ acoustic measurements. Currently, acoustic tomography is used to constructs images of the attenuation such that the spatial dependence and the magnitude of the attenuation can be estimated. Rouseff et al.5 have implemented an acoustic tomography algorithm to invert measured amplitude data to determine the attenuation within a region of bubbly water. They have applied the algorithm to only a portion of the data obtained during the Delta Frame experiment conducted at the Scripps Pier facility. Data run 6 occurred during an otherwise quiescent period and provides a baseline for the background while data runs 5 and 7 occurred during significant wave breaking and rip current activity. Of particular interest is data run 5 because it coincided with experiments of other researchers, which provide independent measurements of the bubble field . The proposed work for FY00 has three components. First, the tomographic analysis initiated by Rouseff et al. on attenuation data from the Delta Frame experiment will be extended to other data runs. Second, the algorithm for the tomographic reconstruction of attenuation will be modified to produce an image of the spatial variation in sound speed.

Subject Categories:

  • Numerical Mathematics
  • Acoustic Detection and Detectors
  • Fluid Mechanics

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