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- Title
- Causality between stock prices and exchange rates: A case of the United States.
- Creator
- Ozair, Amber., Florida Atlantic University, Yuhn, Ky-hyang
- Abstract/Description
-
This thesis investigates the direction of causality as well as short-run dynamics and long-run equilibrium relationship between stock prices and exchange rates using quarterly data for the period 1960:1--2004:4. The studies apply techniques of the unit root, cointegration and Standard Granger causality tests to examine the relationship between these two financial variables. The empirical results reveal that there is no causal linkage and no cointegration between the stock prices and exchange...
Show moreThis thesis investigates the direction of causality as well as short-run dynamics and long-run equilibrium relationship between stock prices and exchange rates using quarterly data for the period 1960:1--2004:4. The studies apply techniques of the unit root, cointegration and Standard Granger causality tests to examine the relationship between these two financial variables. The empirical results reveal that there is no causal linkage and no cointegration between the stock prices and exchange rates as suggested under Traditional and Portfolio approaches. The results support the view that the semi-strong form of EMH holds true for the U.S. financial markets.
Show less - Date Issued
- 2006
- PURL
- http://purl.flvc.org/fcla/dt/13393
- Subject Headings
- Econometric models, Business forecasting--Mathematical models, Efficient market theory, Stock exchanges--Mathematical models
- Format
- Document (PDF)
- Title
- Hydrodynamic analysis of ocean current turbines using vortex lattice method.
- Creator
- Goly, Aneesh, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The main objective of the thesis is to carry out a rigorous hydrodynamic analysis of ocean current turbines and determine power for a range of flow and geometric parameters. For the purpose, a computational tool based on the vortex lattice method (VLM) is developed. Velocity of the flow on the turbine blades, in relation to the freestream velocity, is determined through induction factors. The geometry of trailing vortices is taken to be helicoidal. The VLM code is validated by comparing its...
Show moreThe main objective of the thesis is to carry out a rigorous hydrodynamic analysis of ocean current turbines and determine power for a range of flow and geometric parameters. For the purpose, a computational tool based on the vortex lattice method (VLM) is developed. Velocity of the flow on the turbine blades, in relation to the freestream velocity, is determined through induction factors. The geometry of trailing vortices is taken to be helicoidal. The VLM code is validated by comparing its results with other theoretical and experimental data corresponding to flows about finite-aspect ratio foils, swept wings and a marine current turbine. The validated code is then used to study the performance of the prototype gulfstream turbine for a range of parameters. Power and thrust coefficients are calculated for a range of tip speed ratios and pitch angles. Of all the cases studied, the one corresponding to tip speed ratio of 8 and uniform pitch angle 20 produced the maximum power of 41.3 [kW] in a current of 1.73 [m/s]. The corresponding power coefficient is 0.45 which is slightly less than the Betz limit power coefficient of 0.5926. The VLM computational tool developed for the research is found to be quite efficient in that it takes only a fraction of a minute on a regular laptop PC to complete a run. The tool can therefore be efficiently used or integrated into software for design optimization.
Show less - Date Issued
- 2010
- PURL
- http://purl.flvc.org/FAU/2683131
- Subject Headings
- Marine turbines, Mathematical models, Water currents, Forecasting, Mathematical models, Aerodynamics, Mathematics, Finite element method
- Format
- Document (PDF)
- Title
- Aerodynamic analysis of a propeller in a turbulent boundary layer flow.
- Creator
- Lachowski, Felipe Ferreira., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Simulating the exact chaotic turbulent flow field about any geometry is a dilemma between accuracy and computational resources, which has been continuously studied for just over a hundred years. This thesis is a complete walk-through of the entire process utilized to approximate the flow ingested by a Sevik-type rotor based on solutions to the Reynolds Averaged Navier-Stokes equations (RANS). The Multiple Reference Frame fluid model is utilized by the code of ANSYS-FLUENT and results are...
Show moreSimulating the exact chaotic turbulent flow field about any geometry is a dilemma between accuracy and computational resources, which has been continuously studied for just over a hundred years. This thesis is a complete walk-through of the entire process utilized to approximate the flow ingested by a Sevik-type rotor based on solutions to the Reynolds Averaged Navier-Stokes equations (RANS). The Multiple Reference Frame fluid model is utilized by the code of ANSYS-FLUENT and results are validated by experimental wake data. Three open rotor configurations are studied including a uniform inflow and the rotor near a plate with and without a thick boundary layer. Furthermore, observations are made to determine the variation in velocity profiles of the ingested turbulent flow due to varying flow conditions.
Show less - Date Issued
- 2013
- PURL
- http://purl.flvc.org/fcla/dt/3360798
- Subject Headings
- Acoustical engineering, Boundary layer control, Multiphase flow, Mathematical models, Fluid mechanics, Mathematical models, Turbulence, Mathematical models, Computatioinal fluid dynamics
- Format
- Document (PDF)
- Title
- Efficient leeway drift prediction.
- Creator
- Lee, Yanhua., Florida Atlantic University, Su, Tsung-Chow, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Search and rescue of crafts in distress on the sea surface require the capability to accurately predict the drift of target craft in a short time. A nonlinear mathematical model (original model) has been developed as a tool for the study of the boat drift. Wind load computation considers the wind gradient and the vessel geometry. The current loads include form and friction drag. From the numerical evaluations, the effects of various environmental and vehical parameters on drift are properly...
Show moreSearch and rescue of crafts in distress on the sea surface require the capability to accurately predict the drift of target craft in a short time. A nonlinear mathematical model (original model) has been developed as a tool for the study of the boat drift. Wind load computation considers the wind gradient and the vessel geometry. The current loads include form and friction drag. From the numerical evaluations, the effects of various environmental and vehical parameters on drift are properly accounted for. Simplification of the original model results in a model which is computationally 60 times faster, so-called version 1, without losing much accuracy. In order to meet the needs of two minute prediction for practical implementation, a further simplified model, version 2, was developed from version 1. It is found that the computing speed can be improved one hundred times, and this will facilitate the practical implementation of FAU model in search planning.
Show less - Date Issued
- 1989
- PURL
- http://purl.flvc.org/fcla/dt/14499
- Subject Headings
- Search and rescue operations--Mathematical models, Ocean currents--Mathematical models, Winds--Speed--Mathematical models
- Format
- Document (PDF)
- Title
- A SHORT RUN MACROECONOMETRIC MODEL OF THE GREEK ECONOMY, 1956-1969.
- Creator
- TSOUBLEKAS, GEORGE BASIL., Florida Atlantic University, Scheidell, John M., College of Business, Department of Economics
- Abstract/Description
-
Tho basis of this study is a macroeconometric model of Greece that consists of fifteen equations estimated by ordinary least squares methods from annual data and five definitional aggregates. The model is designed primarily to explain the behavior of the Greek economy from 1953, but it also has value for short run forecasting. A unique feature is the emphasis given to the interplay of imports, investment and exports. The stability test indicates a stable model with a damped oscillation of a...
Show moreTho basis of this study is a macroeconometric model of Greece that consists of fifteen equations estimated by ordinary least squares methods from annual data and five definitional aggregates. The model is designed primarily to explain the behavior of the Greek economy from 1953, but it also has value for short run forecasting. A unique feature is the emphasis given to the interplay of imports, investment and exports. The stability test indicates a stable model with a damped oscillation of a twenty-five period cycle. The predictive ability tests were very favorable and the Durbin-Watson tests indicated low auto-correlation. Future forecasts were made with the use of trend estimated values for the exogenous variables. Finally, the analysis of multipliers was used to evaluate the policy implications of the model.
Show less - Date Issued
- 1973
- PURL
- http://purl.flvc.org/fcla/dt/13596
- Subject Headings
- Macroeconomics--Mathematical models, Greece--Economic policy--Mathematical models, Greece--Economic conditions--Mathematical models
- Format
- Document (PDF)
- Title
- Mathematical modeling of plankton patchiness.
- Creator
- Ather, Simantha S., Noonburg, Erik G., Graduate College
- Date Issued
- 2011-04-08
- PURL
- http://purl.flvc.org/fcla/dt/3164458
- Subject Headings
- Marine plankton, Marine zooplankton, Mathematical models
- Format
- Document (PDF)
- Title
- Fractal ion-channel behavior generates fractal firing patterns in neuronal models.
- Creator
- Liebovitch, Larry S., Lowen, Steven B., White, John A.
- Date Issued
- 1999-05
- PURL
- http://purl.flvc.org/fau/165477
- Subject Headings
- Biophysics--Research, Fractals, Neural networks (Neurobiology)--Mathematical models, Neurons--Mathematical models, Markov processes--Mathematical models, Ion channels--Mathematical models
- Format
- Document (PDF)
- Title
- INVESTMENT SPENDING IN THE UNITED STATES: AN ANALYSIS OF SOME ECONOMETRIC ISSUES.
- Creator
- SADIKU, CHRISTIANAH YEMISI., Florida Atlantic University, Stronge, William B., College of Business, Department of Economics
- Abstract/Description
-
This thesis examines the determinants of that part of national gross fixed investment which is undertaken by the private sector. Any investment process is subject to a number of separate time lags,and as a result, lagged explanatory variables were used in this study to explain the past trends and the recent surge in capital spending. The cashflow and q models distinguished themselves from other models as relatively accurate descriptive of investment spending. It should be noted, however, that...
Show moreThis thesis examines the determinants of that part of national gross fixed investment which is undertaken by the private sector. Any investment process is subject to a number of separate time lags,and as a result, lagged explanatory variables were used in this study to explain the past trends and the recent surge in capital spending. The cashflow and q models distinguished themselves from other models as relatively accurate descriptive of investment spending. It should be noted, however, that the description of investment spending that appears to have worked well in the past does not have to work so well in the future because economic conditions change.
Show less - Date Issued
- 1987
- PURL
- http://purl.flvc.org/fcla/dt/14375
- Subject Headings
- Investments--United States--Mathematical models
- Format
- Document (PDF)
- Title
- MATHEMATICAL MODELING OF CRAFT DRIFT IN AN OCEAN ENVIRONMENT.
- Creator
- KANG, SIN YOUNG., Florida Atlantic University, Su, Tsung-Chow, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A mathematical model, which accounts for the essential effects of environmental loads and vehicle characteristics from a fluid dynamics point of view, is developed to forecast the position of a craft drifting on the sea surface. The study is intended to provide a better understanding of the dynamics of drift and thus to provide a reliable model of drift prediction for use in future search and rescue mission. In the mathematical formulation, three degrees of freedom (surge, sway and yaw) of a...
Show moreA mathematical model, which accounts for the essential effects of environmental loads and vehicle characteristics from a fluid dynamics point of view, is developed to forecast the position of a craft drifting on the sea surface. The study is intended to provide a better understanding of the dynamics of drift and thus to provide a reliable model of drift prediction for use in future search and rescue mission. In the mathematical formulation, three degrees of freedom (surge, sway and yaw) of a craft are analyzed, since they play the most significant role in the drift prediction problem. The governing equations of motions are derived from Newton's law of dynamics and the environmental loads considered are the forces and moments exerted by wind, current and waves. The forces are analyzed in terms of drag, lift, and inertial forces. The moments are obtained by summing the contribution from the above forces. For the computation of the wind loads, the wind gradient as well as craft geometry is accounted for. In the current loads, profile, friction and propeller drags are included. The wave forces are computed by the use of wave spectral density. The formulation includes the effects of craft rotation as well as craft translation. A computer algorithm for the mathematical model is implemented to obtain the numerical result in the time domain. The model is verified by comparing its result with field measurements. For this purpose, a field test was carried out. The agreement between the computed and field measured drift path was excellent. The real time prediction capability of the model was ascertained.
Show less - Date Issued
- 1987
- PURL
- http://purl.flvc.org/fcla/dt/11894
- Subject Headings
- Ships--Hydrodynamics--Mathematical models, Ocean waves
- Format
- Document (PDF)
- Title
- Mathematical model of the dynamics of psychotherapy.
- Creator
- Norman, Michael D., Charles E. Schmidt College of Science, Center for Complex Systems and Brain Sciences
- Abstract/Description
-
This is a novel attempt to produce a rigorous mathematical model of a complex system. The complex system under study is the relationship between therapists and their clients. The success of psychotherapy depends on the nature of the relationship between a therapist and a client. We use dynamical systems theory to model the dynamics of the emotional interaction between a therapist and client. We determine how the therapeutic endpoint and the dynamics of getting there depend on the parameters...
Show moreThis is a novel attempt to produce a rigorous mathematical model of a complex system. The complex system under study is the relationship between therapists and their clients. The success of psychotherapy depends on the nature of the relationship between a therapist and a client. We use dynamical systems theory to model the dynamics of the emotional interaction between a therapist and client. We determine how the therapeutic endpoint and the dynamics of getting there depend on the parameters of the model. ... We describe the emotional state of both the therapist and client with coupled, first order, nonlinear ordinary differential equations (ODE's). The rate of change of the emotional state of the therapist and client is proportional to their previous state, their uninfluenced state when alone, and an influence function which depends on the state of the other person. We formulated influence functions based on the research literature on psychotherapy and the therapeutic alliance. We then determined the critical points from the intersection of the nullclines and used a numerical ODE solver (Matlab ODE113) to compute the trajectories from different initial conditions. ... The results validate this prototypical approach to psychotherapy ; we have shown that human interaction (in the context of psychotherapy) can be quantified and modeled using differential equations.
Show less - Date Issued
- 2012
- PURL
- http://purl.flvc.org/FAU/3358758
- Subject Headings
- Psychotherapist and patient, Mathematical models, Counselor and client, Mathematical models, Therapeutic alliance, Mathematical models, Psychotherapy, Philosophy, Mathematical models, Evidence-based psychotherapy, Transference (Psychology), Countertransference (Psychology)
- Format
- Document (PDF)
- Title
- Numerical Simulation of Marine Hydrokinetic Turbines in Realistic Operating Conditions.
- Creator
- Dunlap, Broc, VanZwieten, James, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
- Abstract/Description
-
Marine Hydrokinetic (MHK) energy is an alternative to address the demand for cleaner energy sources. This study advanced numerical modeling tools and uses these to evaluate the performance of both a Tidal Turbine (TT) and an Ocean Current Turbine (OCT) operating in a variety of conditions. Inflow models are derived with current speeds ranging from 1.5 to 3 m/s and Turbulence Intensities (TI) of 5-15% and integrated into a TT simulation. An OCT simulation representing a commercial scale 20 m...
Show moreMarine Hydrokinetic (MHK) energy is an alternative to address the demand for cleaner energy sources. This study advanced numerical modeling tools and uses these to evaluate the performance of both a Tidal Turbine (TT) and an Ocean Current Turbine (OCT) operating in a variety of conditions. Inflow models are derived with current speeds ranging from 1.5 to 3 m/s and Turbulence Intensities (TI) of 5-15% and integrated into a TT simulation. An OCT simulation representing a commercial scale 20 m diameter turbine moored to the seafloor via underwater cable is enhanced with the capability to ingest Acoustic Doppler Current Profiler (ADCP) data and simulate fault conditions. ADCP measurements collected off the coast of Ft. Lauderdale during Hurricanes Irma and Maria were post-processed and used to characterize the OCT performance. In addition, a set of common faults were integrated into the OCT model to assess the system response in fault-induced scenarios.
Show less - Date Issued
- 2022
- PURL
- http://purl.flvc.org/fau/fd/FA00013962
- Subject Headings
- Turbines, Ocean wave power, Simulations, Mathematical models
- Format
- Document (PDF)
- Title
- Non-separable two dimensional wavelets and their filter banks in polar coordinates.
- Creator
- Andric, Oleg., Florida Atlantic University, Erdol, Nurgun
- Abstract/Description
-
The problems encountered in development and implementation of orthonormal two dimensional wavelet bases and their filter banks in polar coordinates are addressed. These wavelets and filter banks have possible applications in processing signals that are collected by sensors working in the polar coordinate system, such as biomedical and radar generated signals. The relationship between the space of measurable, square-integrable functions on the punctured polar coordinate system L^2(P) and space...
Show moreThe problems encountered in development and implementation of orthonormal two dimensional wavelet bases and their filter banks in polar coordinates are addressed. These wavelets and filter banks have possible applications in processing signals that are collected by sensors working in the polar coordinate system, such as biomedical and radar generated signals. The relationship between the space of measurable, square-integrable functions on the punctured polar coordinate system L^2(P) and space of measurable, square-integrable functions on the rectangular plane L^2(R^2) is developed. This allows us to develop complete wavelet bases in a more convenient and familiar surrounding of L^2(R^2) and to transport this theory to L^2(P). Corresponding filter banks are also developed. The implementation of wavelet analysis of punctured polar plane is discussed. An example of wavelet bases, filter banks, and implementation is provided.
Show less - Date Issued
- 1995
- PURL
- http://purl.flvc.org/fcla/dt/15190
- Subject Headings
- Wavelets (Mathematics), Coordinates, Polar, Signal processing--Mathematical models
- Format
- Document (PDF)
- Title
- AUTOMATIC STABILIZERS DURING STAGFLATION.
- Creator
- MCINTIRE, RICHARD MICHAEL., Florida Atlantic University, Redman, Milton, College of Business, Department of Economics
- Abstract/Description
-
This thesis explored the impact of inflation upon fiscal automatic stabilizers during the 1973-75 recession. Our study confined itself to the three main devices purported to stabilize the U.S. economy automatically: (1) federal personal income tax liability, (2) corporate profits tax liability, and (3) unemployment compensation benefits. A recursive model, similar to that used by Dusenberry, Eckstein, and Fromm to study fiscal automatic stabilizers in the 1957-58 recession, was constructed....
Show moreThis thesis explored the impact of inflation upon fiscal automatic stabilizers during the 1973-75 recession. Our study confined itself to the three main devices purported to stabilize the U.S. economy automatically: (1) federal personal income tax liability, (2) corporate profits tax liability, and (3) unemployment compensation benefits. A recursive model, similar to that used by Dusenberry, Eckstein, and Fromm to study fiscal automatic stabilizers in the 1957-58 recession, was constructed. Our simulation results led us to conclude that there was a substantial reduction in output and employment due to the impact of inflation upon federal personal income tax liability in the 1973-75 recession. We reached a tentative conclusion that the effects of inflation upon output and employment via corporate profits tax liability were negligible. Finally, we concluded that the effects of inflation upon output and employment via unemployment compensation benefits paid were negligible in the recent stagflation.
Show less - Date Issued
- 1978
- PURL
- http://purl.flvc.org/fcla/dt/13919
- Subject Headings
- Economics, Mathematical, United States--Economic conditions--Mathematical models
- Format
- Document (PDF)
- Title
- What is self organization?.
- Creator
- Liebovitch, Larry S.
- Date Issued
- 2006-04 - 2006-08
- PURL
- http://purl.flvc.org/fau/165910
- Subject Headings
- Biomathematics, Biocomplexity, Self-Organizing systems, Cellular automata--mathematical models, Fractals, Molecules--Mathematical models
- Format
- Document (PDF)
- Title
- Design and finite element analysis of an ocean current turbine blade.
- Creator
- Asseff, Nicholas S., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A composite 3 meter ocean current turbine blade has been designed and analyzed using Blade Element Theory (BET) and commercial Finite Element Modeling (FEM) code, ANSYS. It has been observed that using the numerical BET tool created, power production up to 141 kW is possible from a 3 bladed rotor in an ocean current of 2.5 m/s with the proposed blade design. The blade is of sandwich construction with carbon fiber skin and high density foam core. It also contains two webs made of S2-glass for...
Show moreA composite 3 meter ocean current turbine blade has been designed and analyzed using Blade Element Theory (BET) and commercial Finite Element Modeling (FEM) code, ANSYS. It has been observed that using the numerical BET tool created, power production up to 141 kW is possible from a 3 bladed rotor in an ocean current of 2.5 m/s with the proposed blade design. The blade is of sandwich construction with carbon fiber skin and high density foam core. It also contains two webs made of S2-glass for added shear rigidity. Four design cases were analyzed, involving differences in hydrodynamic shape, material properties, and internal structure. Results from the linear static structural analysis revealed that the best design provides adequate stiffness and strength to produce the proposed power without any structural failure. An Eigenvalue Buckling analysis confirmed that the blade would not fail from buckling prior to overstressed laminate failure if the loading was to exceed the Safety Factor.
Show less - Date Issued
- 2009
- PURL
- http://purl.flvc.org/FAU/221944
- Subject Headings
- Marine turbines, Mathematical models, Fluid dynamics, Structural dynamics, Composite materials, Mathematical models
- Format
- Document (PDF)
- Title
- The acoustic far field of a turbulent boundary layer flow calculated from RANS simulations of the flow.
- Creator
- Blanc, Jean-Baptiste., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Boundary layers are regions where turbulence develops easily. In the case where the flow occurs on a surface showing a certain degree of roughness, turbulence eddies will interact with the roughness elements and will produce an acoustic field. This thesis aims at predicting this type of noise with the help of the Computational Fluid Dynamics (CFD) simulation of a wall jet using the Reynolds Average Navier-Stokes (RANS) equations. A frequency spectrum is reconstructed using a representation of...
Show moreBoundary layers are regions where turbulence develops easily. In the case where the flow occurs on a surface showing a certain degree of roughness, turbulence eddies will interact with the roughness elements and will produce an acoustic field. This thesis aims at predicting this type of noise with the help of the Computational Fluid Dynamics (CFD) simulation of a wall jet using the Reynolds Average Navier-Stokes (RANS) equations. A frequency spectrum is reconstructed using a representation of the turbulence with uncorrelated sheets of vorticity. Both aerodynamic and acoustic results are compared to experimental measurements of the flow. The CFD simulation of the flow returns consistent results but would benefit from a refinement of the grid. The surface pressure spectrum presents a slope in the high frequencies close to the experimental spectrum. The far field noise spectrum has a 5dB difference to the experiments.
Show less - Date Issued
- 2009
- PURL
- http://purl.flvc.org/FAU/368611
- Subject Headings
- Computational fluid dynamics, Turbulence, Mathematical models, Fluid mechanics, Mathematical models, Acoustical engineering
- Format
- Document (PDF)
- Title
- Rapid distortion theory for rotor inflows.
- Creator
- Kawashima, Emilia, Glegg, Stewart A. L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
For aerospace and naval applications where low radiated noise levels are a requirement, rotor noise generated by inflow turbulence is of great interest. Inflow turbulence is stretched and distorted as it is ingested into a thrusting rotor which can have a significant impact on the noise source levels. This thesis studies the distortion of subsonic, high Reynolds number turbulent flow, with viscous effects ignored, that occur when a rotor is embedded in a turbulent boundary layer. The analysis...
Show moreFor aerospace and naval applications where low radiated noise levels are a requirement, rotor noise generated by inflow turbulence is of great interest. Inflow turbulence is stretched and distorted as it is ingested into a thrusting rotor which can have a significant impact on the noise source levels. This thesis studies the distortion of subsonic, high Reynolds number turbulent flow, with viscous effects ignored, that occur when a rotor is embedded in a turbulent boundary layer. The analysis is based on Rapid Distortion Theory (RDT), which describes the linear evolution of turbulent eddies as they are stretched by a mean flow distortion. Providing that the gust does not distort the mean flow streamlines the solution for a mean flow with shear is found to be the same as the solution for a mean potential flow with the addition of a potential flow gust. By investigating the inflow distortion of small-scale turbulence for various simple flows and rotor inflows with weak shear, it is shown that RDT can be applied to incompressible shear flows to determine the flow distortion. It is also shown that RDT can be applied to more complex flows modeled by the Reynolds Averaged Navier Stokes (RANS) equations.
Show less - Date Issued
- 2013
- PURL
- http://purl.flvc.org/fau/fd/FA0004030
- Subject Headings
- Computational fluid dynamics, Fluid dynamic measurements, Fluid mechanics -- Mathematical models, Turbulence -- Computer simulation, Turbulence -- Mathematical models
- Format
- Document (PDF)
- Title
- Reliability-based fatigue design of marine current turbine rotor blades.
- Creator
- Hurley, Shaun., College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
- Abstract/Description
-
The study presents a reliability-based fatigue life prediction model for the ocean current turbine rotor blades. The numerically simulated bending moment ranges based on the measured current velocities off the Southeast coast line of Florida over a one month period are used to reflect the short-term distribution of the bending moment ranges for an idealized marine current turbine rotor blade. The 2-parameter Weibull distribution is used to fit the short-term distribution and then used to...
Show moreThe study presents a reliability-based fatigue life prediction model for the ocean current turbine rotor blades. The numerically simulated bending moment ranges based on the measured current velocities off the Southeast coast line of Florida over a one month period are used to reflect the short-term distribution of the bending moment ranges for an idealized marine current turbine rotor blade. The 2-parameter Weibull distribution is used to fit the short-term distribution and then used to obtain the long-term distribution over the design life. The long-term distribution is then used to determine the number of cycles for any given bending moment range. The published laboratory test data in the form of an ε-N curve is used in conjunction with the long-term distribution of the bending moment ranges in the prediction of the fatigue failure of the rotor blade using Miner's rule. The first-order reliability method is used in order to determine the reliability index for a given section modulus over a given design life. The results of reliability analysis are then used to calibrate the partial safety factors for load and resistance.
Show less - Date Issued
- 2011
- PURL
- http://purl.flvc.org/FAU/3183123
- Subject Headings
- Turbines, Blades, Materials, Fatigue, Marine turbines, Mathematical models, Composite materials, Mathematical models, Structural dynamics
- Format
- Document (PDF)
- Title
- Mathematical modeling of wave-current interactions in marine current turbines.
- Creator
- Singh, Amit J., College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
- Abstract/Description
-
The concept of marine current turbines was developed by Peter Fraenkel in the early 1970s. Ever since Fraenkel's efforts to modify and test the technology, several worldwide agencies have been exploiting the technology to retrofit the marine current turbine to their particular application. The marine current turbine has evolved from generating a few kilowatts to a few gigawatts. The present study focuses on a megawatt sized turbine to be located offshore the coast of Ft. Lauderdale, Florida....
Show moreThe concept of marine current turbines was developed by Peter Fraenkel in the early 1970s. Ever since Fraenkel's efforts to modify and test the technology, several worldwide agencies have been exploiting the technology to retrofit the marine current turbine to their particular application. The marine current turbine has evolved from generating a few kilowatts to a few gigawatts. The present study focuses on a megawatt sized turbine to be located offshore the coast of Ft. Lauderdale, Florida. The turbine is to be placed in a similar location as a 20 kW test turbine developed by the Southeast National Marine Renewable Energy Center (SNMREC) at Florida Atlantic University, Dania Beach, FL. Data obtained from the SNMREC is used in the mathematical model. ANSYS FLUENT is chosen as the CFD software to perform wave-current interaction simulation for the present study. The turbine is modeled in SolidWorks, then meshed in ANSYS ICEM CFD, then run in FLUENT. The results obtained are compared to published work by scholarly articles from Fraenkel, Barltrop and many other well known marine energy researchers. The effects of wave height on the turbine operation are analyzed and the results are presented in the form of plots for tip speed ratio and current velocity.
Show less - Date Issued
- 2012
- PURL
- http://purl.flvc.org/FAU/3352832
- Subject Headings
- Wave resistance (Thermodynamics), Structural design, Mathematical models, Laser Doppler velocimetry, Marine turbines, Mathematical models
- Format
- Document (PDF)
- Title
- Mathematical modeling of plankton patchiness.
- Creator
- Ather, Simantha S., Charles E. Schmidt College of Science, Department of Biological Sciences
- Abstract/Description
-
In natural systems, it has been observed that plankton exist in patches rather than in an even distribution across a body of water. However, the mechanisms behind this patchiness are not fully understood. Several previous modeling studies have examined the effects of abiotic and biotic factors on patch structure. Yet these models ignore a key point: zooplankton often undergo diel vertical migration. I have formulated a model that incorporates vertical movement into the Rosezweig-MacArthur (R...
Show moreIn natural systems, it has been observed that plankton exist in patches rather than in an even distribution across a body of water. However, the mechanisms behind this patchiness are not fully understood. Several previous modeling studies have examined the effects of abiotic and biotic factors on patch structure. Yet these models ignore a key point: zooplankton often undergo diel vertical migration. I have formulated a model that incorporates vertical movement into the Rosezweig-MacArthur (R-M) predator-prey model. The R-M model is stable only at a carrying capacity below a critical value. I found that adding vertical movement stabilizes the system even at a high carrying capacity. By analyzing temporal stability and spatial structure, my results show that vertical movement interacts with carrying capacity to determine patch structure.
Show less - Date Issued
- 2009
- PURL
- http://purl.flvc.org/FAU/368615
- Subject Headings
- Marine plankton, Vertical distribution, Marine ecology, Mathematical models, Macroecology, Mathematical models
- Format
- Document (PDF)