A GRANULAR-BASED APPROACH TO THE ACOUSTIC PROPERTIES OF MARINE SEDIMENTS
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Authors
Swartz, Andrew J.
Subjects
granular mechanics
acoustics
Matlab
simulation
acoustics
Matlab
simulation
Advisors
Olson, Derek
Clark, Abram H., IV
Date of Issue
2023-06
Date
Publisher
Monterey, CA; Naval Postgraduate School
Language
Abstract
Understanding and predicting the acoustic behavior of water-saturated marine sediment is fundamental to underwater sensing, navigation, and communication. Data collected from experiments and field measurements show a clear dependence on frequency for both the attenuation coefficient and phase speed. Existing theories, like Biot-Stoll and VGS, can be fit to this data by fitting multiple parameter values that can be difficult to interpret or measure. Additionally, these theories treat the sediment as a continuum. We take a granular-mechanics approach, treating the medium as a large collection of spatially disordered, discrete objects governed by pairwise forces. These forces include a repulsive term due to intergrain contact forces as well as a variety of dissipative forces, including an inelastic component of normal compression at grain-grain contacts that is not included in the existing models of sediment acoustics. Using theoretical analysis and discrete element method simulations, we show that this granular mechanics perspective may be able to explain salient features of the acoustic properties of marine sediments, such as the frequency-dependent phase speed and attenuation. Our results show a granular mechanics perspective may be able to simplify our understanding of sediment acoustics and provide new insights about the grain-scale origins of observed data.
Type
Thesis
Description
Series/Report No
Department
Physics (PH)
Organization
Identifiers
NPS Report Number
Sponsors
Office of Naval Research, Arlington, VA 22203
Funder
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Citation
Distribution Statement
Approved for public release. Distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.