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TRANSMISSION-LINE-MATRIX MODELING OF INHOMOGENEOUS RECTANGULAR WAVEGUIDES AND CAVITIES
Title
TRANSMISSION-LINE-MATRIX MODELING OF INHOMOGENEOUS RECTANGULAR WAVEGUIDES AND CAVITIES.
Creator
Agba, Lawrence C., Florida Atlantic University, Sadiku, Matthew
Abstract/Description
Fortran algorithms were developed to analyze inhomogeneous rectangular waveguides and cavities using the method of transmission-line-matrix. These algorithms were used specifically to determine the field components, impedances, modes, and power decay rates. The computations were done in one, two or three space dimensions and time. Results obtained were compared with analytical results, where possible. In general, the results were found to be in better agreement with the analytical results...
Show moreFortran algorithms were developed to analyze inhomogeneous rectangular waveguides and cavities using the method of transmission-line-matrix. These algorithms were used specifically to determine the field components, impedances, modes, and power decay rates. The computations were done in one, two or three space dimensions and time. Results obtained were compared with analytical results, where possible. In general, the results were found to be in better agreement with the analytical results than the results obtained using other numerical method.
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Date Issued
1987
PURL
http://purl.flvc.org/fcla/dt/14378
Subject Headings
Electromagnetic waves--Mathematical models
Format
Document (PDF)
Numerical simulation of wave energy dissipation in turbulent boundary layers
Title
Numerical simulation of wave energy dissipation in turbulent boundary layers.
Creator
Moneris, Stephanie Sylvie., Florida Atlantic University, Slinn, D. N., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
Shoaling surface waves create turbulent shear flows at the sea-bed and thereby contribute to wave energy dissipation in the bottom boundary layer. Turbulent boundary layers are examined using a high-resolution time-dependent three-dimensional numerical model. Simulations estimate the wave energy dissipation in the boundary layer. Results indicate that turbulence levels are coupled to the wave cycle; accelerating flow organizes the boundary layer structure, decelerating flow destabilizes it...
Show moreShoaling surface waves create turbulent shear flows at the sea-bed and thereby contribute to wave energy dissipation in the bottom boundary layer. Turbulent boundary layers are examined using a high-resolution time-dependent three-dimensional numerical model. Simulations estimate the wave energy dissipation in the boundary layer. Results indicate that turbulence levels are coupled to the wave cycle; accelerating flow organizes the boundary layer structure, decelerating flow destabilizes it and flow reversal induces the strongest turbulent bursts. Details of the flow are functions of the Reynolds number, wave frequency, wave complexity, presence of a mean current, and the flow history of the preceding wave period. Mean flow properties are compared between the three-dimensional model and one-dimensional eddy-viscosity based models. Generally, features of the boundary layer are satisfactorily approximated by the eddy-viscosity models, with accuracy depending on the wave amplitude, period, phase, and other forcing conditions.
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Date Issued
2000
PURL
http://purl.flvc.org/fcla/dt/12692
Subject Headings
Waves--Mathematical models, Turbulent boundary layer--Mathematical models
Format
Document (PDF)
Numerical simulations of the wave bottom boundary layer over sand ripples
Title
Numerical simulations of the wave bottom boundary layer over sand ripples.
Creator
Pierro, Thomas P., Florida Atlantic University, Slinn, D. N., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
Surface gravity waves propagating in the nearshore produce an oscillatory freestream potential flow near the seabed and commonly cause regular two-dimensional sand ripples to be formed. The existence of the ripples causes complex turbulent flows to evolve in the boundary layer, which can dissipate significant energy from the surface waves. A time-dependent DNS model is used to solve the Navier-Stokes equations in three dimensions on a transformed curvilinear grid for specified wave parameters...
Show moreSurface gravity waves propagating in the nearshore produce an oscillatory freestream potential flow near the seabed and commonly cause regular two-dimensional sand ripples to be formed. The existence of the ripples causes complex turbulent flows to evolve in the boundary layer, which can dissipate significant energy from the surface waves. A time-dependent DNS model is used to solve the Navier-Stokes equations in three dimensions on a transformed curvilinear grid for specified wave parameters. When compared to smooth beds, simulations over wavy topographies demonstrate that turbulence is enhanced due to flow separation in the lee of the ripple crests. Shear instabilities during phases of weak flow and vortex shedding in times of strong flow work together to sustain turbulence throughout the wave period. Resulting flows over ripples exhibit an increase in boundary layer thickness and dissipation rates, as energy is lost to viscous effects in maintaining turbulence.
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Date Issued
2001
PURL
http://purl.flvc.org/fcla/dt/12854
Subject Headings
Boundary layer--Mathematical models, Waves--Mathematical models, Sand waves
Format
Document (PDF)
Subsurface flow generated by a steady wind stress applied at the water surface
Title
Subsurface flow generated by a steady wind stress applied at the water surface.
Creator
Gurfinkiel, Lionel., Florida Atlantic University, Dhanak, Manhar R.
Abstract/Description
A turbulent water current induced by winds, through a friction force at the sea surface and subjected to the Coriolis force in shallow water was studied. A Large Eddy Simulation model developed by Zikanov et al. is used to solve the Navier-Stokes equations. To define the bottom boundary condition, a drag coefficient parameter, based on the ideas of Csanady, is used to evaluate the shear stress at the bottom. To find a suitable bottom boundary condition for this LES simulation, several cases...
Show moreA turbulent water current induced by winds, through a friction force at the sea surface and subjected to the Coriolis force in shallow water was studied. A Large Eddy Simulation model developed by Zikanov et al. is used to solve the Navier-Stokes equations. To define the bottom boundary condition, a drag coefficient parameter, based on the ideas of Csanady, is used to evaluate the shear stress at the bottom. To find a suitable bottom boundary condition for this LES simulation, several cases were considered with change in drag coefficient property. The effect of variation in the depth of the water column was also considered. Variation in surface deflection of the current, variation of the mass flux and distribution of eddy viscosity with depth of the water column are determined. The cases are compared with the case of a deep water column. Numerical results are also compared with field observations.
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Date Issued
2003
PURL
http://purl.flvc.org/fcla/dt/13030
Subject Headings
Ocean-atmosphere interaction--Mathematical models, Turbulence, Wind waves--Mathematical models
Format
Document (PDF)
Time-dependent multipath modeling for underwater acoustic wave propagation in shallow water
Title
Time-dependent multipath modeling for underwater acoustic wave propagation in shallow water.
Creator
Boulanger, Florent Jacques., Florida Atlantic University, Beaujean, Pierre-Philippe
Abstract/Description
A novel acoustic wave propagation model has been developed to determine the effects of the ocean variations on the acoustic propagation field, and to determine the signal measured by a receiver at any distance from an omnidirectional source. The model accounts for environmental conditions. First, a stationary estimate of the complex sound attenuation is computed as a function of frequency and location, using the parabolic equation numerical technique. For a given range, the vertical profile...
Show moreA novel acoustic wave propagation model has been developed to determine the effects of the ocean variations on the acoustic propagation field, and to determine the signal measured by a receiver at any distance from an omnidirectional source. The model accounts for environmental conditions. First, a stationary estimate of the complex sound attenuation is computed as a function of frequency and location, using the parabolic equation numerical technique. For a given range, the vertical profile of the attenuation frequency spectrum is decomposed in the wave number domain. A specific Doppler shift is associated with each wave number. The space-frequency attenuation filter obtained is applied to the transmitted signal to create time-frequency selective fading. This model has been used to simulate the performance of the General Purpose Acoustic Modem, which transmits MFSK modulated sequences between 15.6 kHz to 32.1 kHz. The range of operation varies from 1 to 5 km, in 15 meters of water. Experimental data have been collected under sea-state 2 conditions. The model has been successfully validated when compared to experimental data and to the Crepeau model.
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Date Issued
2003
PURL
http://purl.flvc.org/fcla/dt/12978
Subject Headings
Underwater acoustics--Mathematical models, Sound--Transmission, Ocean waves--Mathematical models
Format
Document (PDF)
Dynamic analysis of single- and multi-module platforms in waves
Title
Dynamic analysis of single- and multi-module platforms in waves.
Creator
Kling, Kaylie Ann., Florida Atlantic University, Ananthakrishnan, Palaniswamy, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
The response of single- and multi-module floating platforms to surface waves is investigated theoretically. Wave exciting forces are computed using methods based on the Morrison equation and Froude-Krylov hypothesis. The radiation forces are obtained from experimental results of Vugt and where possible diffraction forces using the Haskind reciprocity relation. Heave and pitch response of a one-module platform and hinge-connected two-module platform are determined by integrating the...
Show moreThe response of single- and multi-module floating platforms to surface waves is investigated theoretically. Wave exciting forces are computed using methods based on the Morrison equation and Froude-Krylov hypothesis. The radiation forces are obtained from experimental results of Vugt and where possible diffraction forces using the Haskind reciprocity relation. Heave and pitch response of a one-module platform and hinge-connected two-module platform are determined by integrating the corresponding equations of rigid-body motion. A structural dynamic analysis is also carried out using the Green's function method to determine the elastic flexural response of the platform to waves. The results are compared with the experimental and numerical findings of others. The thesis contributes to a better understanding of rigid-body and elastic response of large ocean platforms subject to wave forces. The methodology is computationally less intensive and therefore can be effectively used for the design of platforms and the validation of numerical algorithms.
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Date Issued
2006
PURL
http://purl.flvc.org/fcla/dt/13399
Subject Headings
Ocean engineering, Wave motion, Theory of, Water waves--Mathematical models, Drilling platforms, Extreme value theory
Format
Document (PDF)
Design and analysis of hybrid titanium-composite hull structures under extreme wave and slamming loads
Title
Design and analysis of hybrid titanium-composite hull structures under extreme wave and slamming loads.
Creator
Rahman, Md Hafizur, Mahfuz, Hassan, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
A finite element tool has been developed to design and investigate a multi-hull composite ship structure, and a hybrid hull of identical length and beam. Hybrid hull structure is assembled by Titanium alloy (Ti-6Al-4V) frame and sandwich composite panels. Wave loads and slamming loads acting on both hull structures have been calculated according to ABS rules at sea state 5 with a ship velocity of 40 knots. Comparisons of deformations and stresses between two sets of loadings demonstrate that...
Show moreA finite element tool has been developed to design and investigate a multi-hull composite ship structure, and a hybrid hull of identical length and beam. Hybrid hull structure is assembled by Titanium alloy (Ti-6Al-4V) frame and sandwich composite panels. Wave loads and slamming loads acting on both hull structures have been calculated according to ABS rules at sea state 5 with a ship velocity of 40 knots. Comparisons of deformations and stresses between two sets of loadings demonstrate that slamming loads have more detrimental effects on ship structure. Deformation under slamming is almost one order higher than that caused by wave loads. Also, Titanium frame in hybrid hull significantly reduces both deformation and stresses when compared to composite hull due to enhancement of in plane strength and stiffness of the hull. A 73m long hybrid hull has also been investigated under wave and slamming loads in time domain for dynamic analysis.
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Date Issued
2013
PURL
http://purl.flvc.org/fau/fd/FA0004048
Subject Headings
Hulls (Naval architecture) -- Design and construction, Ships -- United States -- Design and construction, Structural dynamics, Water waves -- Mathematical models
Format
Document (PDF)
Home Range and Habitat Use of Juvenile Green Turtlesin a Shallow Tidal Environment
Title
Plane-Wave Scattering of a Periodic Corrugated Cylinder.
Creator
Garcia, Samuel, Bagby, Jonathan Dr., Florida Atlantic University, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
Abstract/Description
In this dissertation, a novel approach to modeling the scattered field of a periodic corrugated cylinder, from an oblique incident planewave, is presented. The approach utilizes radial waveguide approximations for fields within the corrugations, which are point matched to approximated scattered fields outside of the corrugation to solve for the expansion coefficients. The point matching is done with TMz and TEz modes simultaneously, allowing for hybrid modes to exist. The derivation of the...
Show moreIn this dissertation, a novel approach to modeling the scattered field of a periodic corrugated cylinder, from an oblique incident planewave, is presented. The approach utilizes radial waveguide approximations for fields within the corrugations, which are point matched to approximated scattered fields outside of the corrugation to solve for the expansion coefficients. The point matching is done with TMz and TEz modes simultaneously, allowing for hybrid modes to exist. The derivation of the fields and boundary conditions used are discussed in detail. Axial and radial propagating modes for the scattered fields are derived and discussed. Close treatment is given to field equations summation truncation and conversion to matrix form, for numerical computing. A detailed account of the modeling approach using Mathematica® and NCAlgebra for the noncommutative algebra, involved in solving for the expansion coefficients, are also given. The modeling techniques offered provide a full description and prediction of the scattered field of a periodic corrugated cylinder. The model is configured to approximate a smooth cylinder, which is then compared against that of a textbook standard smooth cylinder. The methodology and analysis applied in this research provide a solution for computational electromagnetics, RF communications, Radar systems and the like, for the design, development, and analysis of such systems. Through the rapid modeling techniques developed in this research, early knowledge discovery can be made allowing for better more effective decision making to be made early in the design and investigation process of an RF project.
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Date Issued
2017
PURL
http://purl.flvc.org/fau/fd/FA00004819
Subject Headings
Diffractive scattering., Radio frequency integrated circuits., Electromagnetic waves--Mathematical models., Electromagnetic waves--Diffraction., Electromagnetic waves--Scattering., Fourier transformations., Electromagnetic theory--Mathematical models.
Format
Document (PDF)
Plane-Wave Scattering of a Periodic Corrugated Cylinder
Title
Plane-Wave Scattering of a Periodic Corrugated Cylinder.
Creator
Garcia, Samuel, Bagby, Jonathan, Florida Atlantic University, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
Abstract/Description
In this dissertation, a novel approach to modeling the scattered field of a periodic corrugated cylinder, from an oblique incident planewave, is presented. The approach utilizes radial waveguide approximations for fields within the corrugations, which are point matched to approximated scattered fields outside of the corrugation to solve for the expansion coefficients. The point matching is done with TMz and TEz modes simultaneously, allowing for hybrid modes to exist. The derivation of the...
Show moreIn this dissertation, a novel approach to modeling the scattered field of a periodic corrugated cylinder, from an oblique incident planewave, is presented. The approach utilizes radial waveguide approximations for fields within the corrugations, which are point matched to approximated scattered fields outside of the corrugation to solve for the expansion coefficients. The point matching is done with TMz and TEz modes simultaneously, allowing for hybrid modes to exist. The derivation of the fields and boundary conditions used are discussed in detail. Axial and radial propagating modes for the scattered fields are derived and discussed. Close treatment is given to field equations summation truncation and conversion to matrix form, for numerical computing. A detailed account of the modeling approach using Mathematica® and NCAlgebra for the noncommutative algebra, involved in solving for the expansion coefficients, are also given. The modeling techniques offered provide a full description and prediction of the scattered field of a periodic corrugated cylinder. The model is configured to approximate a smooth cylinder, which is then compared against that of a textbook standard smooth cylinder. The methodology and analysis applied in this research provide a solution for computational electromagnetics, RF communications, Radar systems and the like, for the design, development, and analysis of such systems. Through the rapid modeling techniques developed in this research, early knowledge discovery can be made allowing for better more effective decision making to be made early in the design and investigation process of an RF project.
Show less
Date Issued
2017
PURL
http://purl.flvc.org/fau/fd/FA00004819a
Subject Headings
Diffractive scattering., Radio frequency integrated circuits., Electromagnetic waves--Mathematical models., Electromagnetic waves--Diffraction., Electromagnetic waves--Scattering., Fourier transformations., Electromagnetic theory--Mathematical models.
Format
Document (PDF)