Dissertation
I. Acoustic Line-Scan Imaging of Interface Scattering Effects II. Spectral Analysis of Scattering from Elastic Spherical Shells in Water III. Testing of Low-Frequency Elastic Modes
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000002462
Handle:
https://hdl.handle.net/2376/120305
Abstract
Aspects of acoustic scattering from simple underwater targets are considered in a variety of experimental and theoretical studies. Part I examines a lab experiment of line-scan imaging of the backscattering from a thin spherical shell for two cases: i) near a single flat interface, ii) within an ideal waveguide with an external source/receiver. Geometric ray models are used to describe the backscattering in the time, frequency, and holographic image domains. The holographic image focuses scattered echoes to distinct points in space and time identifiable by ray model, including multiple-scattering effects. Part II examines the theory of scattering from underwater elastic spherical shells, given by the exact solution Partial Wave Series form function. The form function of stainless-steel shells are examined in 2D domains: i) frequency vs. scattering angle domain, ii) frequency vs. thickness domain. The global structure observed in the 2D form functions are explained by ray models describing the interference between the distinct scattering mechanisms: the specular reflection and circumferential surface-guided Lamb waves. Part III examines tank experiments testing the low-frequency modes of a stainless-steel cylinder and a thin spherical shell, using modulated acoustic radiation pressure. The modulation allows a high-frequency focused wave to impart a low-frequency force on an object, driving the object at the resonance frequency of its lowest modes. A hydrophone measures the target response via acoustic radiation, providing a method of testing the elastic mode of the target by two types of scans: a frequency scan in modulation frequency, and a physical scan of the drive point along the object at a fixed modulation frequency.
Metrics
Details
- Title
- I. Acoustic Line-Scan Imaging of Interface Scattering Effects II. Spectral Analysis of Scattering from Elastic Spherical Shells in Water III. Testing of Low-Frequency Elastic Modes
- Creators
- Auberry Renaud Fortuner
- Contributors
- Philip L Marston (Advisor)Nicholas Cerruti (Committee Member)Mathew D Duez (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Physics and Astronomy, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 455
- Identifiers
- 99900606856701842
- Language
- English
- Resource Type
- Dissertation