Two Dimensional Acoustic Propagation Through Oceanic Internal Solitary Waves

Two Dimensional Acoustic Propagation Through Oceanic Internal Solitary Waves
Author:
Publisher:
Total Pages: 65
Release: 2006
Genre: Hydrodynamics
ISBN:

Internal solitary waves, or solitons, are often generated in coastal or continental shelf regions when tidal currents advect stratified water over bathymetric relief, creating an internal tide which non-linearly evolves into one or more solitons. A major consequence of solitons in a stratified environment is the vertical displacement of water parcels which can lead to sound speed variability of order 10m/s with spatial scales of order 100 meters and timescales of order minutes. Thus significant variations in sonar performance on both surface based ships and submarines can be expected. An understanding into the nature of acoustic propagation through these waves is vital for future development of sonar prediction systems. This research investigates acoustic normal mode propagation through solitons using a 2D parabolic equation simulation and weak acoustic scattering theory whose primary physics is a single scatter Bragg mechanism. To simplify the theory, a Gaussian soliton model is developed that compares favorably to the results from a traditional sech2 soliton model. The theory of sound through a Gaussian soliton was then tested against the numerical simulation under conditions of various acoustic frequency, source depths, soliton position relative to the source and soliton number. The theoretical results compare favorably with numerical simulations at 75, 150 and 300-Hz. Higher frequencies need to be tested to determine the limits of the first order theory. Higher order theory will then be needed to address even higher frequencies and to deal with weakly excited modes. This research is the first step in moving from a state of observing acoustic propagation through solitons, to one of predicting it.

Coastal Acoustic Tomography

Coastal Acoustic Tomography
Author: Arata Kaneko
Publisher: Elsevier
Total Pages: 362
Release: 2020-02-05
Genre: Science
ISBN: 0128189428

Coastal Acoustic Tomography begins with the specifics required for designing a Coastal Acoustic Tomography (CAT) experiment and operating the CAT system in coastal seas. Following sections discuss the procedure for data analyses and various application examples of CAT to coastal/shallow seas (obtained in various locations). These sections are broken down into four kinds of methods: horizontal-slice inversion, vertical-slice inversion, modal expansion method and data assimilation. This book emphasizes how dynamic phenomena occurring in coastal/shallow seas can be analyzed using the standard method of inversion and data assimilation. The book is relevant for physical oceanographers, ocean environmentalists and ocean dynamists, focusing on the event being observed rather than the intrinsic details of observational processes. Application examples of successful dynamic phenomena measured by coastal acoustic tomography are also included. Provides the information needed for researchers and graduate students in physical oceanography, ocean-fluid dynamics and ocean environments to apply Ocean Acoustic Tomography (OAT) to their own fields Presents the benefits of using acoustic tomography, including less disturbance to aquatic environments vs. other monitoring methods Includes the assimilation of CAT data into a coastal sea circulation model, a powerful tool to predict coastal-sea environmental changes

Numerical Ocean Acoustic Propagation in Three Dimensions

Numerical Ocean Acoustic Propagation in Three Dimensions
Author: Ding Lee
Publisher: World Scientific
Total Pages: 224
Release: 1995
Genre: Science
ISBN: 9789810223038

This book introduces a comprehensive mathematical formulation of the three-dimensional ocean acoustic propagation problem by means of functional and operator splitting techniques in conjunction with rational function approximations. It presents various numerical solutions of the model equation such as finite difference, alternating direction and preconditioning. The detailed analysis of the concept of 3D, N x 2D and 2D problems is very useful not only mathematically and physically, but also computationally. The inclusion of a complete detailed listing of proven computer codes which have been in use by a number of universities and research organizations worldwide makes this book a valuable reference source. Advanced knowledge of numerical methods, applied mathematics and ocean acoustics is not required to understand this book. It is oriented toward graduate students and research scientists to use for research and application purposes.

Fundamentals of Ocean Acoustics

Fundamentals of Ocean Acoustics
Author: L.M. Brekhovskikh
Publisher: Springer Science & Business Media
Total Pages: 289
Release: 2003-03-18
Genre: Science
ISBN: 0387954678

This book provides an up-to-date introduction to the theory of sound propagation in the ocean. The text treats both ray and wave propagation and pays considerable attention to stochastic problems such as the scattering of sound at rough surfaces and random inhomogeneities. An introductory chapter that discusses the basic experimental data complements the following theoretical chapters. New material has been added throughout for this third edition. New topics covered include: - inter-thermocline lenses and their effect on sound fields - weakly divergent bundles of rays - ocean acoustic tomography - coupled modes - sound scattering by anisotropic volume inhomogeneities with fractal spectra - Voronovich's approach to sound scattering from the rough sea surface. In addition, the list of references has been brought up to date and the latest experimental data have been included.

Sound Propagation through the Stochastic Ocean

Sound Propagation through the Stochastic Ocean
Author: John A. Colosi
Publisher: Cambridge University Press
Total Pages: 443
Release: 2016-06-20
Genre: Mathematics
ISBN: 1107072344

In this book, key discoveries in the field of statistical ocean acoustics over the last 35 years are addressed with illustrations from ocean observations.

Sound Propagation through the Stochastic Ocean

Sound Propagation through the Stochastic Ocean
Author: John A. Colosi
Publisher: Cambridge University Press
Total Pages: 443
Release: 2016-06-20
Genre: Science
ISBN: 1316684032

The ocean is opaque to electromagnetic radiation and transparent to low frequency sound, so acoustical methodologies are an important tool for sensing the undersea world. Stochastic sound-speed fluctuations in the ocean, such as those caused by internal waves, result in a progressive randomisation of acoustic signals as they traverse the ocean environment. This signal randomisation imposes a limit to the effectiveness of ocean acoustic remote sensing, navigation and communication. Sound Propagation through the Stochastic Ocean provides a comprehensive treatment of developments in the field of statistical ocean acoustics over the last 35 years. This will be of fundamental interest to oceanographers, marine biologists, geophysicists, engineers, applied mathematicians, and physicists. Key discoveries in topics such as internal waves, ray chaos, Feynman path integrals, and mode transport theory are addressed with illustrations from ocean observations. The topics are presented at an approachable level for advanced students and seasoned researchers alike.

Three-dimensional Acoustic Propagation Through Shallow Water Internal, Surface Gravity and Bottom Sediment Waves

Three-dimensional Acoustic Propagation Through Shallow Water Internal, Surface Gravity and Bottom Sediment Waves
Author: Alexey Alexandrovich Shmelev
Publisher:
Total Pages: 193
Release: 2011
Genre: Acoustic models
ISBN:

This thesis describes the physics of fully three-dimensional low frequency acoustic interaction with internal waves, bottom sediment waves and surface swell waves that are often observed in shallow waters and on continental slopes. A simple idealized model of the ocean waveguide is used to analytically study the properties of acoustic normal modes and their perturbations due to waves of each type. The combined approach of a semi-quantitative study based on the geometrical acoustics approximation and on fully three-dimensional coupled mode numerical modeling is used to examine the azimuthal dependence of sound wave horizontal reflection from, transmission through and ducting between straight parallel waves of each type. The impact of the natural crossings of nonlinear internal waves on horizontally ducted sound energy is studied theoretically and modeled numerically using a three-dimensional parabolic equation acoustic propagation code. A realistic sea surface elevation is synthesized from the directional spectrum of long swells and used for three-dimensional numerical modeling of acoustic propagation. As a result, considerable normal mode amplitude scintillations were observed and shown to be strongly dependent on horizontal azimuth, range and mode number. Full field numerical modeling of low frequency sound propagation through large sand waves located on a sloped bottom was performed using the high resolution bathymetry of the mouth of San Francisco Bay. Very strong acoustic ducting is shown to steer acoustic energy beams along the sand wave's curved crests.

Acoustic Interactions with Submerged Elastic Structures

Acoustic Interactions with Submerged Elastic Structures
Author: A. Guran
Publisher: World Scientific
Total Pages: 398
Release: 2001
Genre: Technology & Engineering
ISBN: 9789812811950

The interaction of acoustic fields with submerged elastic structures, both by propagation and scattering, is being investigated at various institutions and laboratories world-wide with ever-increasing sophistication of experiments and analysis. This book offers a collection of contributions from these research centers that represent the present state-of-the-art in the study of acoustic elastic interaction, being on the cutting edge of these investigations. This includes the description of acoustic scattering from submerged elastic objects and shells by the Resonance Scattering Theory of Flax, Dragonette and berall, and the interaction of these phenomena in terms of interface waves. It also includes the use of this theory for the purpose of inverse scattering, i.e. the determination of the scattered objects properties from the received acoustic backscattered signals. The problem of acoustically excited waves in inhomogeneous and anisotropic materials, and of inhomogeneous propagating waves is considered. Vibrations and resonances of elastic shells, including shells with various kinds of internal attachments, are analyzed. Acoustic scattering experiments are described in the time domain, and on the basis of the WignerOCoVille distribution. Acoustic propagation in the water column over elastic boundaries is studied experimentally both in laboratory tanks, and in the field, and is analyzed theoretically. Ultrasonic nondestructive testing, including such aspects like probe modelling, scattering by various types of cracks, receiving probes and calibration by a side-drilled hole is also studied in details. A comprehensive picture of these complex phenomena and other aspects is presented in the book by researchers that are experts in each of these domains, giving up-to-date accounts of the field in all these aspects. Contents: Discrete Spectral Analysis for Solitary Waves (J Engelbrecht et al.); Propagation and Interaction of Waves in Nonlinear-Elastic Solids with Microstructures (V I Erofeyev); Matched Field Processing: A Powerful Tool for the Study of Oceans and Scatterers (A Tolstoy); Progress in Underwater Acoustic Modeling (P C Etter); Reflectivity Response of a Submerged Layer with Density, Sound Velocity and Absorbtion Gradients (R Carb-Fit(r)); Mathematical Aspects of Wave Phenomena in a Wave Guide with Elastic Walls and Operator Polynomials (B P Belinskiy & J P Dauer); On Some General Mathematical Properties of the System Elastic Plate OCo Acoustic Medium (B P Belinskiy); Acoustic Scattering from Finite Length Cylinders Encapped by Two Hemispheres (D Decultot et al.); Acoustic Scattering from a Circular Cylindrical Shell Immersed in Water. Generation and Reradiation of Guided Waves (F L(r)on & G Maze); The Finite Element/Boundary Element Approach to the Radiation and Scattering of Submerged Shells Including Internal Structure or Equipment (R Miller); Resonance Extraction, Phase Matching Method and the Surface Paths for Finite Elastic Cylinders (X-L Bao); Nonlinear Waves in Thermoelastic Solids Undergoing Phase Transitions (J K Knowles). Readership: Nonlinear scientists."