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Title: The effect of sea surface motion on underwater communication systems.
Creator: Strutt, Guenael Thomas., Florida Atlantic University, LeBlanc, Lester R., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Underwater acoustic communications are significantly affected by time-varying multipath. Time-delays induced by multiple reactors on boundaries can be compensated for through equalization, and good transmission can be achieved. However, soundwaves reflected from moving scatterers on the sea surface undergo slight variations in frequency that significantly degrade the performance of communication devices. Ocean data was collected to evaluate the amount of Doppler-spread induced by wind-driven...
Show moreUnderwater acoustic communications are significantly affected by time-varying multipath. Time-delays induced by multiple reactors on boundaries can be compensated for through equalization, and good transmission can be achieved. However, soundwaves reflected from moving scatterers on the sea surface undergo slight variations in frequency that significantly degrade the performance of communication devices. Ocean data was collected to evaluate the amount of Doppler-spread induced by wind-driven surface waves. A model for the shallow water acoustic channel is discussed and implemented using a simplified approach to the gaussian-beam ray-tracing algorithm. This leads to the definition of the spreading function, a convenient tool to describe fading channels. The spreading function serves as a reference for the simulation of a classic digital communication setup, using baseband antipodal equalization. It is shown how frequency-spreading, a consequence of sea surface motion, affects the resulting error rate.
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Date Issued: 1999
PURL: http://purl.flvc.org/fcla/dt/15675
Subject Headings: Underwater acoustics, Acoustic surface waves
Format: Document (PDF)

Title: Experiments for Waves Breaking Over a Three-Dimensional Submerged Bar.
Creator: Roy, Travis L., Seiffert, Betsy, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The influence of monochromatic waves interacting with a submerged bar structure is investigated through laboratory experiments in a wave flume. Wave profiles for a range of non-breaking, spilling, and plunging waves were analyzed for three offshore water depths through the interpretation of wave gauge and video imagery data. Evolution of propagating waves was reflected in data which showed increased amplitudes due to shoaling with subsequent breaking, transfer of single frequency spectrum...
Show moreThe influence of monochromatic waves interacting with a submerged bar structure is investigated through laboratory experiments in a wave flume. Wave profiles for a range of non-breaking, spilling, and plunging waves were analyzed for three offshore water depths through the interpretation of wave gauge and video imagery data. Evolution of propagating waves was reflected in data which showed increased amplitudes due to shoaling with subsequent breaking, transfer of single frequency spectrum from lower to higher frequency harmonics, and dissipation of energy after breaking onset. Comparisons of collected experimental data with previous theory developed by Yao et al (2013), Smith & Kraus (1991), Galvin (1968) for wave classification showed to be relatively accurate for both relative submergence and surf similarity methods. Wave breaking onset identified by instability in the wave crests allowed for measurements of breaking wave height and depth at breaking. Theory by Johnson (2006) and Goda (1974) compared to experimental data showed little agreement for predicting breaking wave heights.
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Date Issued: 2018
PURL: http://purl.flvc.org/fau/fd/FA00013096
Subject Headings: Water waves., Water waves--Measurement., Surface waves.
Format: Document (PDF)

$Boundary-integral analysis of nonlinear diffraction forces on a submerged body$

Title: Boundary-integral analysis of nonlinear diffraction forces on a submerged body.
Creator: Vinayan, Vimal., Florida Atlantic University, Ananthakrishnan, Palaniswamy, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A three-dimensional nonlinear time-dependent boundary-integral algorithm is developed to compute wave forces on an underwater vehicle. The effect of viscosity is neglected and the cases for which the effects could be important are discussed. The present algorithm is however an efficient tool to determine wave forces on a submerged body and can also be integrated into a viscous flow algorithm. A numerical wave tank is constructed for the simulation. A damping layer is introduced to minimize...
Show moreA three-dimensional nonlinear time-dependent boundary-integral algorithm is developed to compute wave forces on an underwater vehicle. The effect of viscosity is neglected and the cases for which the effects could be important are discussed. The present algorithm is however an efficient tool to determine wave forces on a submerged body and can also be integrated into a viscous flow algorithm. A numerical wave tank is constructed for the simulation. A damping layer is introduced to minimize spurious reflection of scattered waves at the open boundary. A sinusoidal progressive pressure patch is used to generate incident waves. Wave forces are determined using four different methods: viz., (1) Froude-Krylov volume integration method, (2) Froude-Krylov surface pressure integration method, (3) Linear diffraction analysis and (4) Nonlinear diffraction analysis for a range of parameters including incident wavelength and wave height. Results are compared to quantify effects of nonlinearity and diffraction effect of the body.
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Date Issued: 2003
PURL: http://purl.flvc.org/fcla/dt/13048
Subject Headings: Waves--Diffraction, Boundary element methods, Hydrodynamics, Surface waves (Oceanography)
Format: Document (PDF)

Title: Design and testing of an untethered vertically ascending profiler for use in measuring near-surface turbulence.
Creator: Bogin, Jeffrey Isaac., Florida Atlantic University, Dhanak, Manhar R.
Abstract/Description: The Vertically Ascending Micro-scale Profiler, or VAMP, has been designed, constructed, and tested to be used in conjunction with FAU's Turbulence Package in order to collect vertical turbulence profiles close to the free surface. Unique to VAMP is that it has been specifically designed as an untethered ascending profiler. Examination of turbulence data collected using VAMP shows that the measured shear spectrum and the turbulent kinetic energy dissipation closely matches the Nasmyth Spectrum...
Show moreThe Vertically Ascending Micro-scale Profiler, or VAMP, has been designed, constructed, and tested to be used in conjunction with FAU's Turbulence Package in order to collect vertical turbulence profiles close to the free surface. Unique to VAMP is that it has been specifically designed as an untethered ascending profiler. Examination of turbulence data collected using VAMP shows that the measured shear spectrum and the turbulent kinetic energy dissipation closely matches the Nasmyth Spectrum. Data processing techniques made it possible to filter out motion generated by surface wave action, which allowed VAMP to collect data at depths as shallow as the troughs of the surface waves. VAMP can be launched, deployed several times, and recovered all within a thirty minute time frame by a crew of four.
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Date Issued: 2003
PURL: http://purl.flvc.org/fcla/dt/13020
Subject Headings: Turbulence--Measurement, Surface waves (Oceanography)
Format: Document (PDF)

Title: Modelling of underwater ambient noise due to whitecaps.
Creator: Elisseeff, Pierre., Florida Atlantic University, Glegg, Stewart A. L.
Abstract/Description: A theoretical model accounting for underwater ambient noise due to whitecap-generated bubbles and drop-impacts is developed to investigate the possible mechanisms of ocean noise generation. A general analysis is laid down, leading to expressions of the noise spectrum in an undefined environment. Subsequently the cases of isovelocity and stratified deep oceans are considered, and specific expressions are derived. The stratified deep ocean estimations of the directional spectrum are then...
Show moreA theoretical model accounting for underwater ambient noise due to whitecap-generated bubbles and drop-impacts is developed to investigate the possible mechanisms of ocean noise generation. A general analysis is laid down, leading to expressions of the noise spectrum in an undefined environment. Subsequently the cases of isovelocity and stratified deep oceans are considered, and specific expressions are derived. The stratified deep ocean estimations of the directional spectrum are then compared to experimental data and a good agreement is found. Finally the absolute noise levels due to bubbles and drop impacts are discussed, and bubble noise is found to be larger than drop impact noise. The collective bubble oscillation hypothesis is also discussed, and although clues are given for and against this hypothesis no rigorous justification for this has been found.
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Date Issued: 1992
PURL: http://purl.flvc.org/fcla/dt/14784
Subject Headings: Underwater acoustics--Measurement, Acoustic surface waves
Format: Document (PDF)

Title: Radius distribution of ocean near surface bubbles.
Creator: Auffret, Yvan., Florida Atlantic University, Glegg, Stewart A. L.
Abstract/Description: This study proposed to determine an ocean surface bubble radius distribution using theoretical noise models, experimental noise spectral data and a theoretical model for the bubble size distribution. The obtained distribution was compared to previous experimental distributions. A good agreement was found for the radius upper cut-off but the shape and the peak radius of the distribution are different from experimental observations. The most probable reasons for these differences were given....
Show moreThis study proposed to determine an ocean surface bubble radius distribution using theoretical noise models, experimental noise spectral data and a theoretical model for the bubble size distribution. The obtained distribution was compared to previous experimental distributions. A good agreement was found for the radius upper cut-off but the shape and the peak radius of the distribution are different from experimental observations. The most probable reasons for these differences were given. Moreover, the validity of recent theoretical bubble noise models was checked. Eventually, the main limitations of the study were pointed out and directions for future works were given.
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Date Issued: 1993
PURL: http://purl.flvc.org/fcla/dt/14922
Subject Headings: Underwater acoustics, Acoustic surface waves, Bubbles
Format: Document (PDF)

Title: Boundary reflection coefficient estimation from depth dependence of the acoustic Green's function.
Creator: Conrad, Alexander., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Sound propagation in a waveguide is greatly dependent on the acoustic properties of the boundaries. The effect of these properties can be described by a bottom reflection coefficient RB, and surface reflection coefficient RS. Two methods for estimating reflection coefficients are used in this research. The first, the ratio method, is based on the variations of the Green's function with depth utilizing the ratio of the wavenumber spectra at two depths. The second, the pole method, is based on...
Show moreSound propagation in a waveguide is greatly dependent on the acoustic properties of the boundaries. The effect of these properties can be described by a bottom reflection coefficient RB, and surface reflection coefficient RS. Two methods for estimating reflection coefficients are used in this research. The first, the ratio method, is based on the variations of the Green's function with depth utilizing the ratio of the wavenumber spectra at two depths. The second, the pole method, is based on the wavenumbers of the modal peaks in the spectrum at a particular depth. A method to invert for sound speed and density is also examined. Estimates of RB and RS based on synthetic data by the ratio method were very close to their predicted values, especially for higher frequencies and longer apertures. The pole method returned less precise estimates though with longer apertures, the estimates were better. Using experimental data, results of the pole method as well a geoacoustic inversion technique based on them were mixed. The ratio method was used to estimate RS based on the actual data and returned results close to the predicted phase of p.
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Date Issued: 2010
PURL: http://purl.flvc.org/FAU/3164094
Subject Headings: Underwater acoustics, Acoustic surface waves, Green's functions, Electromagnetic waves, Mathematics, Wave equation, Numerical solutions
Format: Document (PDF)

Title: Modeling of shallow water ambient noise directionality using the effective depth approximation.
Creator: Galletta, Frank Anton., Florida Atlantic University, Glegg, Stewart A. L.
Abstract/Description: A theoretical model has been developed to compute the vertical array directional response for surface generated ambient noise in a shallow water environment. The cross spectrum function is based on a normal mode solution to the wave equation in which the effective depth approximation is used to yield closed form solutions for two distinct mode types. The effective depth modes encompass the shallowest grazing angles where the bottom reacts as a pressure release surface to the incident plane...
Show moreA theoretical model has been developed to compute the vertical array directional response for surface generated ambient noise in a shallow water environment. The cross spectrum function is based on a normal mode solution to the wave equation in which the effective depth approximation is used to yield closed form solutions for two distinct mode types. The effective depth modes encompass the shallowest grazing angles where the bottom reacts as a pressure release surface to the incident plane waves. The rigid bottom solution takes over as the grazing angle increases and attenuation becomes significant. The computed vertical array beam output was compared to other models including a fast field wavenumber integration method and a multipath eigenray method with mixed results. The results indicated good agreement for both comparisons with the realization that the effective depth model is sensitive to the approximation discontinuity at the mode transition point.
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Date Issued: 1996
PURL: http://purl.flvc.org/fcla/dt/15237
Subject Headings: Underwater acoustics--Measurement, Noise--Measurement, Acoustic surface waves
Format: Document (PDF)

Title: A study of ambient noise in shallow water.
Creator: Pirie, Rachel Louise., Florida Atlantic University, Glegg, Stewart A. L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis describes a series of measurements that took place over the duration of one year on the South Florida Testing Facility (SFTF) range, Dania, in order to survey the shallow water ambient acoustic environment. Three groups of data sets were taken in December 1998, May 1999 and July 1999. The data was collected using the Ambient Noise Sonar (ANS) that was developed in the Ocean Engineering department at Florida Atlantic University. The ambient acoustic environment was found to be...
Show moreThis thesis describes a series of measurements that took place over the duration of one year on the South Florida Testing Facility (SFTF) range, Dania, in order to survey the shallow water ambient acoustic environment. Three groups of data sets were taken in December 1998, May 1999 and July 1999. The data was collected using the Ambient Noise Sonar (ANS) that was developed in the Ocean Engineering department at Florida Atlantic University. The ambient acoustic environment was found to be highly variable with two main components. Boat noise was found to primarily be associated with the inlet and a source of snapping shrimp situated on the shallow water 30ft reef became apparent through 24hr observation. The effects of adverse weather were not studied due to the absence of this source during the measurement periods.
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Date Issued: 1999
PURL: http://purl.flvc.org/fcla/dt/15738
Subject Headings: Underwater acoustics, Noise--Measurement, Acoustic surface waves
Format: Document (PDF)

Title: Geoacoustic inversion of subbottom channels using mulitple frequency input parameters.
Creator: Weeks, Rebecca., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis investigates inversion techniques used to determine the geoacoustic properties of a shallow-water waveguide. The data used were obtained in the Shallow Water '06 Modal Mapping Experiment in which four buoys drifted over a system of subbottom channels. The method used was perturbative inversion using modal eigenvalues as input parameters, which were found using an autoregressive spectral estimator. This work investigates the differences between a "channel" region and a "no channel"...
Show moreThis thesis investigates inversion techniques used to determine the geoacoustic properties of a shallow-water waveguide. The data used were obtained in the Shallow Water '06 Modal Mapping Experiment in which four buoys drifted over a system of subbottom channels. The method used was perturbative inversion using modal eigenvalues as input parameters, which were found using an autoregressive spectral estimator. This work investigates the differences between a "channel" region and a "no channel" region based on an inferred stratigraphic model. Inversions were performed on data from a single buoy both at individual frequencies and multiple frequencies simultaneously. Since the use of multiple frequencies and a certain set of constraints proved to be an effective method of inversion, the method was applied to data from the other three buoys as well. It is shown that the "channel" and "no channel" regions have significantly different sound speed profiles.
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Date Issued: 2010
PURL: http://purl.flvc.org/FAU/1930486
Subject Headings: Oceanographic buoys, Stochastic processes, Acoustic surface waves, Underwater acoustics, Wave equation, Numerical solutions
Format: Document (PDF)

Title: Hydrodynamic analysis of underwater bodies for efficient station keeping in shallow waters with surface waves.
Creator: Bradley, Matthew, Ananthakrishnan, Palaniswamy, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: To determine the effect of body shape on the response of underwater vehicles to surface waves in shallow water, the wave radiation hydrodynamic forces are evaluated for a family of (i) prolate spheroidal hull forms and (ii) cylindrical bodies with hemispherical nose and conical tail sections by systematically varying the geometric parameters but keeping displacement constant. The added-mass and wave damping coefficients are determined using a frequency-domain, simple-source based boundary...
Show moreTo determine the effect of body shape on the response of underwater vehicles to surface waves in shallow water, the wave radiation hydrodynamic forces are evaluated for a family of (i) prolate spheroidal hull forms and (ii) cylindrical bodies with hemispherical nose and conical tail sections by systematically varying the geometric parameters but keeping displacement constant. The added-mass and wave damping coefficients are determined using a frequency-domain, simple-source based boundary integral method. Results are obtained for a range of wave frequencies and depths of vehicle submergence all for a fixed water depth of 10 m. With the wave exciting force and moment determined using the Froude-Krylov theory, the response transfer functions for heave and pitch are then determined. The heave and pitch response spectra in actual littoral seas are then determined with the sea state modeled using TMA spectral relations. Results show that vehicle slenderness is a key factor affecting the hydrodynamic coefficients and response. The results show two characteristics that increase the radiation hydrodynamic forces corresponding to heave and pitch motions: namely, vehicle length and further-away from mid-vehicle location of the body shoulder. The opposite is true for the oscillatory surge motion. By utilizing these observed characteristics, one can design the lines for maximum radiation forces and consequently minimum hull response for the critical modes of rigid-body motion in given waters and vehicle missions. In the studies carried out in the thesis, a hull with a long parallel middle body with hemispherical nose and conical tail sections has better heave and pitch response characteristics compared prolate spheroid geometry of same volume. The methodology developed herein, which is computationally efficient, can be used to determine optimal hull geometry for minimal passive vehicle response in a given sea.
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Date Issued: 2014
PURL: http://purl.flvc.org/fau/fd/FA00004084, http://purl.flvc.org/fau/fd/FA00004084
Subject Headings: Oceanographic submersibles -- Hydrodynamics, Surface waves (Oceanography) -- Mathematical models, Wave motion, Theory of
Format: Document (PDF)

Title: Acoustic Tonal and Vector Properties of Red Hind Grouper Vocalizationd.
Creator: Matthews, Cameron Anthony, Beaujean, Pierre-Philippe, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Vertebrates are the most prodigious vocalizing animals in existence, and the most diverse methods of acoustic communication among vertebrates can be found in the ocean. Relatively many teleost fish are gifted with the ability to communicate acoustically, and the family of serranidae often performs this as a function of the swim bladder. Epinephelus Guttatus (E. guttatus), or more commonly the red hind grouper, is equipped with a drum shaped swim bladder acting as a monopole under typical...
Show moreVertebrates are the most prodigious vocalizing animals in existence, and the most diverse methods of acoustic communication among vertebrates can be found in the ocean. Relatively many teleost fish are gifted with the ability to communicate acoustically, and the family of serranidae often performs this as a function of the swim bladder. Epinephelus Guttatus (E. guttatus), or more commonly the red hind grouper, is equipped with a drum shaped swim bladder acting as a monopole under typical ocean conditions. This configuration allows for what is understood to be omnidirectional projection of tones approximately centered between 40 and 440 Hz and spanning anywhere from 40 to 200 Hz of bandwidth and modulation effects based on observed data provided by researchers. Prior studies on many other fish show correlation in acoustic communication profile with length, size and sexual identity. In the red hind, sexual dimorphism leads to an inherent female identity in all juvenile fish which converts to male according to environmental factors, recommending at least consistent organs across both sexes be assumed even if not in use. Much research has been performed on male fish vocalization in terms of spectral content. Communication in fish is a complex multi-modal process, with acoustic communication being important for many of the species, particularly those in the littoral regions of the worlds’ oceans. If identifying characteristics of the red hind vocalization can be isolated based on detection, classification, tracking and localizing methodologies, then these identifying characteristics may indeed lead to passive feature identification that allows for estimation of individual fish mass. Hypotheses based on vector, cyclostationary and classical tonal mechanics are presented for consideration. A battery of test data collection events, applying pre-recorded fish vocalizations to a geolocated undersea sound source were conducted. The results are supplied with the intent of validating hypothesis in a non-expert system manner that shows how a series of biological metrics may be assessed for detection, classification, localization and mass estimation for an individual vocalizing red hind grouper
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Date Issued: 2017
PURL: http://purl.flvc.org/fau/fd/FA00004826, http://purl.flvc.org/fau/fd/FA00004826
Subject Headings: Wave-motion, Theory of., Sound production by animals., Fishes--Vocalization., Bioacoustics., Animal communication., Underwater acoustics., Acoustic surface waves.
Format: Document (PDF)

Title: An Investigation into the Acoustic Variability and the Attenuation of an Acoustic Signal within a Port Environment Focusing on Port Everglades, Florida.
Creator: Sheahan, Daniel, Frisk, George V., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A methodology for characterizing the acoustical properties of a port environment, namely Port Everglades, has been proposed and carried out. This approach includes both a port-wide analysis of how the basic oceanographic features within the port impact the acoustic properties, and also a more focused sampling methodology within a small region of Port Everglades, allowing for the acoustic characteristics, including ambient noise, and an approximate signal absorption to be computed. The results...
Show moreA methodology for characterizing the acoustical properties of a port environment, namely Port Everglades, has been proposed and carried out. This approach includes both a port-wide analysis of how the basic oceanographic features within the port impact the acoustic properties, and also a more focused sampling methodology within a small region of Port Everglades, allowing for the acoustic characteristics, including ambient noise, and an approximate signal absorption to be computed. The results documented through the duration of this research indicate that the temperature variation throughout the port is the principal contributor to the characteristics of the sound velocity profile. Ambient noise measurements have revealed high levels of background noise within the sub-5 kHz region, owing likely to consistent port traffic. The calculation of absorption indicates that high frequency systems, i.e. > 100 kHz, may encounter problems when transmitting over a considerable distance. These are important factors for consideration when implementing a successful underwater acoustic system.
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Date Issued: 2007
PURL: http://purl.flvc.org/fau/fd/FA00012553
Subject Headings: Underwater acoustics--Measurement, Port Everglades (Fort Lauderdale, Fla), Harbors--Environmental aspects--Florida--Fort Lauderdale, Acoustic surface waves--Measurement
Format: Document (PDF)

Acoustic surface waves (7)	+ -
Underwater acoustics (5)	+ -
Underwater acoustics--Measurement (3)	+ -
Noise--Measurement (2)	+ -
Numerical solutions (2)	+ -

Surface waves (Oceanography) (2)	+ -
Wave equation (2)	+ -
Acoustic surface waves--Measurement (1)	+ -
Acoustic surface waves. (1)	+ -
Animal communication. (1)	+ -
Bioacoustics. (1)	+ -
Boundary element methods (1)	+ -
Bubbles (1)	+ -
Electromagnetic waves (1)	+ -
Fishes--Vocalization. (1)	+ -
Green's functions (1)	+ -
Harbors--Environmental aspects--Florida--Fort Lauderdale (1)	+ -
Hydrodynamics (1)	+ -
Mathematics (1)	+ -
Oceanographic buoys (1)	+ -
Oceanographic submersibles -- Hydrodynamics (1)	+ -
Port Everglades (Fort Lauderdale, Fla) (1)	+ -
Sound production by animals. (1)	+ -
Stochastic processes (1)	+ -
Surface waves (Oceanography) -- Mathematical models (1)	+ -
Surface waves. (1)	+ -
Turbulence--Measurement (1)	+ -
Underwater acoustics. (1)	+ -
Water waves--Measurement. (1)	+ -
Water waves. (1)	+ -

Florida Atlantic University (11)	+ -
College of Engineering and Computer Science (9)	+ -
Department of Ocean and Mechanical Engineering (9)	+ -
Glegg, Stewart A. L. (4)	+ -
Ananthakrishnan, Palaniswamy (2)	+ -

Auffret, Yvan. (1)	+ -
Beaujean, Pierre-Philippe (1)	+ -
Bogin, Jeffrey Isaac. (1)	+ -
Bradley, Matthew (1)	+ -
Conrad, Alexander. (1)	+ -
Dhanak, Manhar R. (1)	+ -
Elisseeff, Pierre. (1)	+ -
Frisk, George V. (1)	+ -
Galletta, Frank Anton. (1)	+ -
LeBlanc, Lester R. (1)	+ -
Matthews, Cameron Anthony (1)	+ -
Pirie, Rachel Louise. (1)	+ -
Roy, Travis L. (1)	+ -
Seiffert, Betsy (1)	+ -
Sheahan, Daniel (1)	+ -
Strutt, Guenael Thomas. (1)	+ -
Vinayan, Vimal. (1)	+ -
Weeks, Rebecca. (1)	+ -

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