Dissertation
Acoustic scattering enhancements for partially-exposed cylinders in sand and at a free surface caused by Franz waves and other processes
Doctor of Philosophy (PhD), Washington State University
01/2014
Handle:
https://hdl.handle.net/2376/111280
Abstract
The exact partial-wave series solution for scattering from a circular cylinder half-exposed at a free surface was converted from the frequency domain to the time domain, which revealed three scattering features which matched the timing of Franz waves, a family of creeping subsonic waves along a curved surface. The three features correspond to the three possible paths a Franz wave can take along a cylinder, reflecting off the surface in front of the cylinder zero, one, or two times.
Sand was degassed and transferred to a sandbox in a water tank. The sound speed in the sand was predicted by the material properties of the sand. A stainless-steel and an aluminum cylinder were buried to various exposures in the sandbox. Receiver scans revealed refracted rays into the sand, and a numerical method was used to plot timing curves to these features and thus empirically determine the sound speed.
Receiver scans of the two cylinders at one-eighth, one-fourth, and one-half exposure confirmed that Franz waves were present for a cylinder on sand. The Franz features were generally stronger for lower exposure, and were often enhanced by the placement of a brass plate behind the cylinders.
Receiver scans of the aluminum cylinder at the air-water interface showed the presence of Franz waves, which were stronger for lower exposure. Target scans of the cylinder at the interface for various grazing angles also showed Franz features.
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Details
- Title
- Acoustic scattering enhancements for partially-exposed cylinders in sand and at a free surface caused by Franz waves and other processes
- Creators
- Anthony Ryan Smith
- Contributors
- Philip L Marston (Advisor)Matthew D Duez (Committee Member)Matthew D McCluskey (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Physics and Astronomy, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 364
- Identifiers
- 99900581843001842
- Language
- English
- Resource Type
- Dissertation