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Title: Detection, localization, and identification of bearings with raceway defect for a dynamometer using high frequency modal analysis of vibration across an array of accelerometers.
Creator: Waters, Nicholas., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis describes a method to detect, localize and identify a faulty bearing in a rotating machine using narrow band envelope analysis across an array of accelerometers. This technique is developed as part of the machine monitoring system of an ocean turbine. A rudimentary mathematical model is introduced to provide an understanding of the physics governing the vibrations caused by a bearing with a raceway defect. This method is then used to detect a faulty bearing in two setups : on a...
Show moreThis thesis describes a method to detect, localize and identify a faulty bearing in a rotating machine using narrow band envelope analysis across an array of accelerometers. This technique is developed as part of the machine monitoring system of an ocean turbine. A rudimentary mathematical model is introduced to provide an understanding of the physics governing the vibrations caused by a bearing with a raceway defect. This method is then used to detect a faulty bearing in two setups : on a lathe and in a dynamometer.
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3359156
Subject Headings: Marine turbines, Mathematical models, Vibration, Measurement, Fluid dynamics, Dynamic testing
Format: Document (PDF)

Title: Wavelet de-noising applied to vibrational envelope analysis methods.
Creator: Bertot, Edward Max, Khoshgoftaar, Taghi M., Beaujean, Pierre-Philippe, Florida Atlantic University, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
Abstract/Description: In the field of machine prognostics, vibration analysis is a proven method for detecting and diagnosing bearing faults in rotating machines. One popular method for interpreting vibration signals is envelope demodulation, which allows a technician to clearly identify an impulsive fault source and its severity. However incipient faults -faults in early stages - are masked by in-band noise, which can make the associated impulses difficult to detect and interpret. In this thesis, Wavelet De...
Show moreIn the field of machine prognostics, vibration analysis is a proven method for detecting and diagnosing bearing faults in rotating machines. One popular method for interpreting vibration signals is envelope demodulation, which allows a technician to clearly identify an impulsive fault source and its severity. However incipient faults -faults in early stages - are masked by in-band noise, which can make the associated impulses difficult to detect and interpret. In this thesis, Wavelet De-Noising (WDN) is implemented after envelope-demodulation to improve accuracy of bearing fault diagnostics. This contrasts the typical approach of de-noising as a preprocessing step. When manually measuring time-domain impulse amplitudes, the algorithm shows varying improvements in Signal-to-Noise Ratio (SNR) relative to background vibrational noise. A frequency-domain measure of SNR agrees with this result.
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Date Issued: 2014
PURL: http://purl.flvc.org/fau/fd/FA00004080, http://purl.flvc.org/fau/fd/FA00004080
Subject Headings: Fluid dynamics, Signal processing, Structural dynamics, Wavelet (Mathematics)
Format: Document (PDF)

Title: Software framework for prognostic health monitoring of ocean-based power generation.
Creator: Bowren, Mark., College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
Abstract/Description: On August 5, 2010 the U.S. Department of Energy (DOE) has designated the Center for Ocean Energy Technology (COET) at Florida Atlantic University (FAU) as a national center for ocean energy research and development of prototypes for open-ocean power generation. Maintenance on ocean-based machinery can be very costly. To avoid unnecessary maintenance it is necessary to monitor the condition of each machine in order to predict problems. This kind of prognostic health monitoring (PHM) requires a...
Show moreOn August 5, 2010 the U.S. Department of Energy (DOE) has designated the Center for Ocean Energy Technology (COET) at Florida Atlantic University (FAU) as a national center for ocean energy research and development of prototypes for open-ocean power generation. Maintenance on ocean-based machinery can be very costly. To avoid unnecessary maintenance it is necessary to monitor the condition of each machine in order to predict problems. This kind of prognostic health monitoring (PHM) requires a condition-based maintenance (CBM) system that supports diagnostic and prognostic analysis of large amounts of data. Research in this field led to the creation of ISO13374 and the development of a standard open-architecture for machine condition monitoring. This thesis explores an implementation of such a system for ocean-based machinery using this framework and current open-standard technologies.
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3342035
Subject Headings: Machinery, Monitoring, Marine turbines, Mathematical models, Fluid dynamics, Structural dynamics
Format: Document (PDF)

Title: Dynamic stability of fluid-conveying pipes on uniform or non-uniform elastic foundations.
Creator: Vittori, Pablo J., Florida Atlantic University, Elishakoff, Isaac, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The dynamic behavior of straight cantilever pipes conveying fluid is studied, establishing the conditions of stability for systems, which are only limited to move in a 2D-plane. Internal friction of pipe and the effect of the surrounding fluid are neglected. A universal stability curve showing boundary between the stable and unstable behaviors is constructed by finding solution to equation of motion by exact and high-dimensional approximate methods. Based on the Boobnov-Galerkin method, the...
Show moreThe dynamic behavior of straight cantilever pipes conveying fluid is studied, establishing the conditions of stability for systems, which are only limited to move in a 2D-plane. Internal friction of pipe and the effect of the surrounding fluid are neglected. A universal stability curve showing boundary between the stable and unstable behaviors is constructed by finding solution to equation of motion by exact and high-dimensional approximate methods. Based on the Boobnov-Galerkin method, the critical velocities for the fluid are obtained by using both the eigenfunctions of a cantilever beam (beam functions), as well as the utilization of Duncan's functions. Stability of cantilever pipes with uniform and non-uniform elastic foundations of two types are considered and discussed. Special emphasis is placed on the investigation of the paradoxical behavior previously reported in the literature.
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Date Issued: 2004
PURL: http://purl.flvc.org/fcla/dt/13167
Subject Headings: Strains and stresses, Structural dynamics, Structural stability, Fluid dynamics, Vibration
Format: Document (PDF)

Title: Intrusion of warm hyper-pycnal plumes in shelfwaters of the Exuma Cays.
Creator: Pitts, Patrick A., Harbor Branch Oceanographic Institute
Date Issued: 2002
PURL: http://purl.flvc.org/fau/fd/FA00007089
Subject Headings: Exuma (Bahamas), Continental shelf, Plumes (Fluid dynamics), Coral bleaching
Format: Document (PDF)

Title: Empirical Analysis of the Dissipated Acoustic Energy in Wave Breaking.
Creator: Francke, Kristina, Dhanak, Manhar, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: In this research an attempt is made at explaining the physical processes behind energy dissipation during wave breaking, through spectral analysis of the resulting sound. The size of an air bubble can be directly linked to the frequency of the sound that is heard using the simple harmonic solution to the Rayleigh–Plesset equation. It indicates the inverse relationship between frequency and bubble size. And this relationship has been used to identify wave breaking in general [MANASSEH 2006]....
Show moreIn this research an attempt is made at explaining the physical processes behind energy dissipation during wave breaking, through spectral analysis of the resulting sound. The size of an air bubble can be directly linked to the frequency of the sound that is heard using the simple harmonic solution to the Rayleigh–Plesset equation. It indicates the inverse relationship between frequency and bubble size. And this relationship has been used to identify wave breaking in general [MANASSEH 2006]. Now this research goes a step farther and looks at how the frequency spectrum of the sound changes with time, in an effort to understand the general pattern and from that to deduce an empirical equation that describes the breaking down of turbulence during a wave breaking event. Two main processes have been identified, with the second process having three main indicators that are necessary to evidence wave breaking. The first process is a near instantaneous shattering of the initial air bubble into much smaller metastable bubbles of a size that appears to be common for all waves independent of wave height. Then in the second process, the bubbles continue to break down following a recognisable pattern.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013504
Subject Headings: Waves, Energy dissipation, Spectral analysis, Fluid dynamics, Acoustic energy
Format: Document (PDF)

Title: Effect of wind on near-shore breaking waves.
Creator: Schaffer, Faydra., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The aim of this project is to identify the effect of wind on near-shore breaking waves. A breaking wave was created using a simulated beach slope configuration. Testing was done on two different beach slope configurations. The effect of offshore winds of varying speeds was considered. Waves of various frequencies and heights were considered. A parametric study was carried out. The experiments took place in the Hydrodynamics lab at FAU Boca Raton campus. The experimental data validates the...
Show moreThe aim of this project is to identify the effect of wind on near-shore breaking waves. A breaking wave was created using a simulated beach slope configuration. Testing was done on two different beach slope configurations. The effect of offshore winds of varying speeds was considered. Waves of various frequencies and heights were considered. A parametric study was carried out. The experiments took place in the Hydrodynamics lab at FAU Boca Raton campus. The experimental data validates the knowledge we currently know about breaking waves. Offshore winds effect is known to increase the breaking height of a plunging wave, while also decreasing the breaking water depth, causing the wave to break further inland. Offshore winds cause spilling waves to react more like plunging waves, therefore increasing the height of the spilling wave while consequently decreasing the breaking water depth.
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Date Issued: 2010
PURL: http://purl.flvc.org/FAU/2979378
Subject Headings: Wave motion, Theory of, Ocean waves, Climatology, Computational fluid dynamics
Format: Document (PDF)

Title: A Computational Analysis of Bio-Inspired Modified Boundary Layers for Acoustic Pressure Shielding in A Turbulent Wall Jet.
Creator: Gonzalez, Alexander J., Glegg, Stewart, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Surface pressure fluctuations developed by turbulent flow within a boundary layer is a major cause of flow noise from a body and an issue which reveals itself over a wide range of engineering applications. Modified boundary layers (MBLs) inspired by the down coat of an owl’s wing has shown to reduce the acoustic effects caused by flow noise. This thesis investigates the mechanisms that modified boundary layers can provide for reducing the surface pressure fluctuations in a boundary layer....
Show moreSurface pressure fluctuations developed by turbulent flow within a boundary layer is a major cause of flow noise from a body and an issue which reveals itself over a wide range of engineering applications. Modified boundary layers (MBLs) inspired by the down coat of an owl’s wing has shown to reduce the acoustic effects caused by flow noise. This thesis investigates the mechanisms that modified boundary layers can provide for reducing the surface pressure fluctuations in a boundary layer. This study analyzes various types of MBLs in a wall jet wind tunnel through computational fluid dynamics and numerical surface pressure spectrum predictions. A novel surface pressure fluctuation spectrum model is developed for use in a wall jet boundary layer and demonstrates high accuracy over a range of Reynolds numbers. Non-dimensional parameters which define the MBL’s geometry and flow environment were found to have a key role in optimizing the acoustic performance.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013209
Subject Headings: Turbulent flow, Turbulent boundary layer, Computational fluid dynamics, Wall jets
Format: Document (PDF)

Title: Numerical models to simulate underwater turbine noise levels.
Creator: Lippert, Renee'., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This work incorporates previous work done by Guerra and the application of fluid dynamics. The structure attached to the turbine will cause unsteady fluctuations in the flow, and ultimately affect the acoustic pressure. The work of Guerra is based on a lot of assumptions and simplifications to the geometry of the turbine and structure. This work takes the geometry of the actual turbine, and uses computational fluid dynamic software to numerically model the flow around the turbine structure....
Show moreThis work incorporates previous work done by Guerra and the application of fluid dynamics. The structure attached to the turbine will cause unsteady fluctuations in the flow, and ultimately affect the acoustic pressure. The work of Guerra is based on a lot of assumptions and simplifications to the geometry of the turbine and structure. This work takes the geometry of the actual turbine, and uses computational fluid dynamic software to numerically model the flow around the turbine structure. Varying the angle of the attack altered the results, and as the angle increased the noise levels along with the sound pulse, and unsteady loading increased. Increasing the number of blades and reducing the chord length both reduced the unsteady loading.
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3355622
Subject Headings: Underwater acoustics, Mathematical models, Turbines, Vibration, Mathematical models, Fluid dynamics
Format: Document (PDF)

Title: Very high frequency MIMO underwater acoustic communications in ports and shallow waters.
Creator: Real, Gaultier., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis presents the development of a Multiple-Input Multiple-Output (MIMO) capable high bit rate acoustic modem operating at high frequencies. A MIMO channel estimation technique based on Least-Squares (LS) estimation is developed here. Channel deconvolution is completed using a Minimum Mean-Square Error (MMSE) Linear Equalizer (LE). An Interference Cancellation Linear Equalizer (ICLE) is used to provide the theoretical limit of the MIMO deconvolution process. The RMSE of the channel...
Show moreThis thesis presents the development of a Multiple-Input Multiple-Output (MIMO) capable high bit rate acoustic modem operating at high frequencies. A MIMO channel estimation technique based on Least-Squares (LS) estimation is developed here. Channel deconvolution is completed using a Minimum Mean-Square Error (MMSE) Linear Equalizer (LE). An Interference Cancellation Linear Equalizer (ICLE) is used to provide the theoretical limit of the MIMO deconvolution process. The RMSE of the channel estimation process was 1.83 % and 6.1810 %, respectively for simulated and experimental data. Using experimental data, the RMSE before MIMO deconvolution process was 141.3 % and dropped down to 60.224 % and to 4.4545 %, respectively after LE and ICLE. At raw reception, the RMSE was 101.83 % and dropped down to 9.36 % and to 1.86 % using respectively LE and ICLE with simulated data.
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Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3333309
Subject Headings: MIMO systems, Wireless communication systems, Underwater acoustics, Fluid dynamics
Format: Document (PDF)

Title: Seakeeping response of a Surface Effect Ship in near-shore transforming seas.
Creator: Kindel, Michael., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Scale model tests are conducted of a Surface Effect Ship in a near-shore developing sea. A beach is built and installed in a wave tank, and a wavemaker is built and installed in the same wave tank. This arrangement is used to simulate developing sea conditions and a 1:30 scale model SES is used for a series of experiments. Pitch and heave measurements are used to investigate the seakeaping response of the vessel in developing seas. The air-cushion pressure and the vessel speed are varied, and...
Show moreScale model tests are conducted of a Surface Effect Ship in a near-shore developing sea. A beach is built and installed in a wave tank, and a wavemaker is built and installed in the same wave tank. This arrangement is used to simulate developing sea conditions and a 1:30 scale model SES is used for a series of experiments. Pitch and heave measurements are used to investigate the seakeaping response of the vessel in developing seas. The air-cushion pressure and the vessel speed are varied, and the seakeeping results are compared as functions of these two parameters. The experiment results show a distinct correlation between the air-cushion pressure and the response amplitude of both pitch and heave. The results of these experiments are compared against results of a computer model of a Surface Effect Ship (SES).
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3355563
Subject Headings: Naval architecture, Fluid dynamics, Wave motion, Theory of, Ships, Hydrodynamics
Format: Document (PDF)

Title: Boundary Layer Control on a Circular Cylindrical Body through Oscillating Lorentz Forcing.
Creator: Seltzer, Ryan K., Dhanak, Manhar R., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Boundary layer control on a circular cylindrical body through oscillating Lorentz forcing is studied by means of numerical simulation of the vorticity-stream function formulation of the Navier-Stokes equations. The model problem considers axisymmetric seawater flow along an infinite cylinder controlled by an idealized radially directed Lorentz force oscillating spatially and temporally. Under optimum forcing parameters, it is shown that sustainable Lorentz induced vortex rings can travel...
Show moreBoundary layer control on a circular cylindrical body through oscillating Lorentz forcing is studied by means of numerical simulation of the vorticity-stream function formulation of the Navier-Stokes equations. The model problem considers axisymmetric seawater flow along an infinite cylinder controlled by an idealized radially directed Lorentz force oscillating spatially and temporally. Under optimum forcing parameters, it is shown that sustainable Lorentz induced vortex rings can travel along the cylinder at a speed equivalent to the phase speed of forcing . Wall stress is shown to locally change sign in the region adjacent to the vortex, considerably decreasing net viscous drag . Adverse flow behaviors are revealed as a result of studying the effects of the Reynolds numbers, strength of the Lorentz force, and phase speed of forcing for boundary layer control. Adverse flow behaviors inc I ude complex vortex configurations found for suboptimal forcing resulting in a considerable increase in wall stress.
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Date Issued: 2007
PURL: http://purl.flvc.org/fau/fd/FA00012549
Subject Headings: Mathematical physics, Lorentz transformations, Boundary layer control, Fluid dynamics
Format: Document (PDF)

Title: Experimental study of flow over a bundle of cylinders.
Creator: Khuc, Hiep Hieu., Florida Atlantic University, Su, Tsung-Chow, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The drag reduction by vortex fusion was investigated. A comparison of flow over a bundle of cylinders in uniform and in disturbed currents was performed in a water channel. The model was subjected to cross flow. A thin cylindrical wire located nearby upstream and leveled at half the height of the test model was used as a source of disturbance. A hydrogen bubble technique was utilized to observe the flow pattern. The accumulation of vortices at stagnating regions in front of a bundle of...
Show moreThe drag reduction by vortex fusion was investigated. A comparison of flow over a bundle of cylinders in uniform and in disturbed currents was performed in a water channel. The model was subjected to cross flow. A thin cylindrical wire located nearby upstream and leveled at half the height of the test model was used as a source of disturbance. A hydrogen bubble technique was utilized to observe the flow pattern. The accumulation of vortices at stagnating regions in front of a bundle of cylinders transformed into a counter-rotated curl at leading edges of each leading cylinder in the bundle. Measurements were carried out by a computerized data acquisition system. Drag coefficient measurements, digital spectral and fourier analyses were also performed. Results have shown that a drag reduction can be obtained by introducing a thin cylindrical wire in front of the stagnation.
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Date Issued: 1994
PURL: http://purl.flvc.org/fcla/dt/15026
Subject Headings: Vortex-motion, Fluid dynamics, Cylinders, Fourier transformations, Hydrodynamics
Format: Document (PDF)

Title: Tearing of an aligned vortex by a current difference in two-layer quasi-geostrophic flow.
Creator: Parthasarathy, Balaji., Florida Atlantic University, Marshall, Jeffrey S., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A study of two-layer quasi-geostrophic vortex flow is performed to determine the effect of a current difference between the layers on a vortex initially extending through both the layers. In particular, the conditions under which the current difference can 'tear' the vortex are examined. In the first set of flows studied, the current difference is generated by a (stronger) third vortex in the upper layer located at a large distance from the (weaker) vortex under study. A set of flows are also...
Show moreA study of two-layer quasi-geostrophic vortex flow is performed to determine the effect of a current difference between the layers on a vortex initially extending through both the layers. In particular, the conditions under which the current difference can 'tear' the vortex are examined. In the first set of flows studied, the current difference is generated by a (stronger) third vortex in the upper layer located at a large distance from the (weaker) vortex under study. A set of flows are also considered in which an ambient geostrophic current difference is produced by a non-uniform background potential vorticity field. The results of the study will be useful in determining the conditions under which large geophysical vortex structures, such as cyclones and ocean rings, can extend to large depths even though the mean currents in the ambient flow change significantly along the vortex length.
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Date Issued: 1993
PURL: http://purl.flvc.org/fcla/dt/14909
Subject Headings: Vortex-motion, Fluid dynamics, Boundary layer control, Flow visualization
Format: Document (PDF)

Title: GALLOPING OF AN ELASTICALLY SUPPORTED BLUFF BODY IN TURBULENT FLOW.
Creator: Li, Qiang, Florida Atlantic University, Lin, Y. K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The phenomenon of flow-induced vibration is found in many engineering systems. The fluid flow generates forces on the structure that cause motion of the structure. In turn, the structural motion changes the angle of attack between the flow and the structure, hence the forces on the structure. Furthermore, turbulence generally exists in a natural fluid flow; namely, the fluid velocity contains a random part. Thus, the problem is formulated as a nonlinear system under random excitations. This...
Show moreThe phenomenon of flow-induced vibration is found in many engineering systems. The fluid flow generates forces on the structure that cause motion of the structure. In turn, the structural motion changes the angle of attack between the flow and the structure, hence the forces on the structure. Furthermore, turbulence generally exists in a natural fluid flow; namely, the fluid velocity contains a random part. Thus, the problem is formulated as a nonlinear system under random excitations. This thesis is focused on one type of motion known as galloping. A mathematical model for the motion of an elastically supported square cylinder in turbulent flow is developed. The physical nonlinear equation is converted to ideal stochastic differential equations of the Ito type using the stochastic averaging method. The probability density for the motion amplitude and the values for the most probable amplitudes are obtained for various mean flow velocities and turbulence levels.
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Date Issued: 1987
PURL: http://purl.flvc.org/fcla/dt/14361
Subject Headings: Random vibration--Mathematical models, Turbulence, Fluid dynamics
Format: Document (PDF)

Title: A model of the horseshoe vortex in juncture flows.
Creator: Monnier, Elie Bertrand., Florida Atlantic University, Dhanak, Manhar R., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: When a boundary-layer flow, either laminar or turbulent, encounters a hemispherical body extending from a surface, a horseshoe-shaped vortex forms at the juncture. In this thesis, we study the evolution of this vortex using a numerical inviscid model and laboratory experiments. The numerical model is based on determining the evolution of the filament using the cut-off method. The assumption is that although the generation of the vortex depends on viscous effects, the dynamic evolution is well...
Show moreWhen a boundary-layer flow, either laminar or turbulent, encounters a hemispherical body extending from a surface, a horseshoe-shaped vortex forms at the juncture. In this thesis, we study the evolution of this vortex using a numerical inviscid model and laboratory experiments. The numerical model is based on determining the evolution of the filament using the cut-off method. The assumption is that although the generation of the vortex depends on viscous effects, the dynamic evolution is well described by inviscid equations of motion. It is found that the vortex filament is fairly steady on the upstream side but on the downstream side, travelling waves appear on it which cannot be suppressed through evolution. For a range of Reynolds number, steady horseshoe-shaped vortex was obtained in the experiments, revealing the shape past the hemisphere. This is compared with the numerical results.
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Date Issued: 1996
PURL: http://purl.flvc.org/fcla/dt/15326
Subject Headings: Boundary layer, Cascades (Fluid dynamics), Flow visualization, Vortex generators
Format: Document (PDF)

Title: Stability of an elliptical vortex in a time-dependent strain field.
Creator: Marshall, Marilyn P., Florida Atlantic University, Dhanak, Manhar R., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A theoretical study of the stability of two-dimensional elliptical vortices in a time-dependent, periodically varying external straining flow was conducted. The mean value of the oscillating straining flow was chosen so that the vortex would be stationary in the absence of fluctuations of the external field about the mean. If the frequency of straining is near to the natural frequency of the vortex for small-amplitude oscillations of the vortex core, so that the vortex is forced near its...
Show moreA theoretical study of the stability of two-dimensional elliptical vortices in a time-dependent, periodically varying external straining flow was conducted. The mean value of the oscillating straining flow was chosen so that the vortex would be stationary in the absence of fluctuations of the external field about the mean. If the frequency of straining is near to the natural frequency of the vortex for small-amplitude oscillations of the vortex core, so that the vortex is forced near its natural frequency, a resonance occurs such that the aspect ratio of the elliptical core boundary initially oscillates with an amplitude that increases linearly with time. After an initial period of growth, the aspect ratio will either follow a bounded limit cycle at large time or it will elongate exponentially with time. The nonlinear evolution of the vortex at large time is studied numerically, and distinct regions of behavior in the parameter space for the vortex are obtained.
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Date Issued: 1992
PURL: http://purl.flvc.org/fcla/dt/14817
Subject Headings: Vortex--Motion, Fluid dynamics--Mathematical models
Format: Document (PDF)

Title: THEORETICAL ANALYSIS OF HEAT EXCHANGERS IN AN OCEAN THERMAL ENERGY CONVERSION SYSTEM.
Creator: BENTON, DUDLEY JAMES., Florida Atlantic University, Tennant, Jeffrey S.
Abstract/Description: A theoretical study was conducted to determine the relationships between the major controlling factors in the heat exchangers in an Ocean Thermal Energy Conversion system. A digital computer model was developed to simulate and analyze the system. Variations in the thermophysical properties of the seawater and working fluid were considered in the analysis. Effects of variation in excess temperature differential on phase change heat transfer rates were also considered. The net power output of...
Show moreA theoretical study was conducted to determine the relationships between the major controlling factors in the heat exchangers in an Ocean Thermal Energy Conversion system. A digital computer model was developed to simulate and analyze the system. Variations in the thermophysical properties of the seawater and working fluid were considered in the analysis. Effects of variation in excess temperature differential on phase change heat transfer rates were also considered. The net power output of the system was determined from a Rankine cycle analysis. The results of this investigation show the necessity of a Rankine cycle analysis and the inclusion of fluid property variations. A significant difference can be seen in the net power output of such a system per dollar invested in the heat exchangers projected by this analysis and the analysis of other investigators which have not considered these factors.
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Date Issued: 1977
PURL: http://purl.flvc.org/fcla/dt/13875
Subject Headings: Heat exchangers--Fluid dynamics, Ocean thermal power plants
Format: Document (PDF)

Title: EXPLORING UNDULATORY SWIMMING BEHAVIORS WITH DEEP REINFORCEMENT LEARNING.
Creator: Alvaro, Alejandro, Verma, Siddhartha, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
Abstract/Description: The capability to navigate in the proximity of solid surfaces while avoiding collision and maintaining high efficiency is essential for the effective design and operation of underwater vehicles. The underlying capability involves a variety of challenges, and a potential approach to overcome such obstacles is to rely on biomimetic or bio-inspired design. Through evolution, organisms have developed methods of locomotion optimized for their specific environment. One of the common forms of...
Show moreThe capability to navigate in the proximity of solid surfaces while avoiding collision and maintaining high efficiency is essential for the effective design and operation of underwater vehicles. The underlying capability involves a variety of challenges, and a potential approach to overcome such obstacles is to rely on biomimetic or bio-inspired design. Through evolution, organisms have developed methods of locomotion optimized for their specific environment. One of the common forms of locomotion found in underwater organisms is undulatory swimming. These undulatory swimmers display different swimming behaviors based on the flow conditions in their environment. These behaviors take advantage of changes in the flow field caused by the presence of obstructions and obstacles upstream or adjacent to the swimmer. For example, a free swimmer in near-proximity to a flat plane can experience changes in lift and drag during locomotion. The reduced drag can benefit the swimmer, however, changes in lift may lead to a collision with obstacles. Despite the abundance of qualitative data from observing these undulatory swimmers, there is a lack of quantitative data, creating a disconnect in understanding how these organisms have evolved to exploit the presence of walls and obstacles. By employing a combination of traditional computational fluid dynamics and novel neural network-based techniques it is possible to emulate the evolution of learned behavior in biological organisms. The current work uses deep reinforcement learning coupled with two-dimensional numerical simulations of self-propelled swimmers to better understand behavior observed in nature.
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Date Issued: 2024
PURL: http://purl.flvc.org/fau/fd/FA00014402
Subject Headings: Reinforcement learning, Computational fluid dynamics, Autonomous underwater vehicles
Format: Document (PDF)

Title: Evaluation of motion compensated ADV measurements for quantifying velocity fluctuations.
Creator: Lovenbury, James William., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This study assesses the viability of using a towfish mounted ADV for quantifying water velocity fluctuations in the Florida Current relevant to ocean current turbine performance. For this study a motion compensated ADV is operated in a test flume. Water velocity fluctuations are generated by a 1.3 cm pipe suspended in front of the ADV at relative current speeds of 0.9 m/s and 0.15 m/s, giving Reynolds numbers on the order of 1000. ADV pitching motion of +/- 2.5 [degree] at 0.3 Hz and a heave...
Show moreThis study assesses the viability of using a towfish mounted ADV for quantifying water velocity fluctuations in the Florida Current relevant to ocean current turbine performance. For this study a motion compensated ADV is operated in a test flume. Water velocity fluctuations are generated by a 1.3 cm pipe suspended in front of the ADV at relative current speeds of 0.9 m/s and 0.15 m/s, giving Reynolds numbers on the order of 1000. ADV pitching motion of +/- 2.5 [degree] at 0.3 Hz and a heave motion of 0.3 m amplitude at 0.2 Hz are utilized to evaluate the motion compensation approach. The results show correction for motion provides up to an order of magnitude reduction in turbulent kinetic energy at frequencies of motion while the IMU is found to generate 2% error at 1/30 Hz and 9% error at 1/60 Hz in turbulence intensity.
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Date Issued: 2013
PURL: http://purl.flvc.org/fcla/dt/3362482
Subject Headings: Motion control systems, Fluid dynamic measurements, Fluid mechanics, Mathematical models, Analysis of covariance
Format: Document (PDF)

FAU Theses and Dissertations (85)	+ -
HBOI Faculty Contributions (4)	+ -
FAU Graduate Student Research (1)	+ -

Fluid dynamics (53)	+ -
Mathematical models (23)	+ -
Computational fluid dynamics (15)	+ -
Structural dynamics (15)	+ -
Marine turbines (13)	+ -

Testing (8)	+ -
Vortex-motion (7)	+ -
Design and construction (6)	+ -
Turbulence (6)	+ -
Vibration (5)	+ -
Boundary layer control (4)	+ -
Flow visualization (4)	+ -
Fluid dynamic measurements (4)	+ -
Fluid mechanics -- Mathematical models (4)	+ -
Hydrodynamics (4)	+ -
Turbines (4)	+ -
Turbulence -- Mathematical models (4)	+ -
Aerodynamic noise (3)	+ -
Cascades (Fluid dynamics) (3)	+ -
Computational fluid dynamics. (3)	+ -
Data processing (3)	+ -
Fluid mechanics (3)	+ -
Mathematical physics (3)	+ -
Measurement (3)	+ -
Rotors (3)	+ -
Structural dynamics. (3)	+ -
Turbulence--Mathematical models. (3)	+ -
Underwater acoustics (3)	+ -
Unsteady flow (Fluid dynamics) (3)	+ -
Wave motion, Theory of (3)	+ -

Florida (2)	+ -
Boynton Inlet (1)	+ -
Everglades (1)	+ -
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