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 Title
 Determination of Hydrodynamic Coefficients of MultiHull Ships for Seakeeping Analysis.
 Creator
 Chafin, Jesse Ryan, Ananthakrishnan, Palaniswamy, Florida Atlantic University
 Abstract/Description

Linear and nonlinear hydrodynamic coefficients of single and multiple hulls are obtained using the boundaryintegral method. For linear frequencydomain analysis, the boundaryintegral method based on a simple source distribution (Yeung [50] was used. The nonlinear time domain simulations were carried out using a boundaryintegral algorithm based on the mixed EulerianLagrangian (MEL) formulation (LonguetHiggins and Cokelet (19] ). Also, linear time domain simulations were carried out by...
Show moreLinear and nonlinear hydrodynamic coefficients of single and multiple hulls are obtained using the boundaryintegral method. For linear frequencydomain analysis, the boundaryintegral method based on a simple source distribution (Yeung [50] was used. The nonlinear time domain simulations were carried out using a boundaryintegral algorithm based on the mixed EulerianLagrangian (MEL) formulation (LonguetHiggins and Cokelet (19] ). Also, linear time domain simulations were carried out by utilizing a simplified mixed EulerianLagrangian formulation and the steadystate results compared with that obtained from linearfrequency domain analysis. Both 2D and 3D results were obtained for a range of parameters such as beam/draft, hullseparation/beam ratios and frequency and amplitude of hull motions. The results shed light on complex wavebody interactions involved in multihull ships and identifY critical hydrodynamic and geometric parameters affecting their sea keeping performance. The computational tools developed and the findings thus contribute to design of multihull ships for improved atsea performance.
Show less  Date Issued
 2007
 PURL
 http://purl.flvc.org/fau/fd/FA00012511
 Subject Headings
 ShipsSeakeepingMathematical models, Stability of ships, ShipsHydrodynamics
 Format
 Document (PDF)
 Title
 ANALYSIS OF HYDRODYNAMIC INTERACTIONS BETWEEN SHIPS IN CONFINED WATERS.
 Creator
 Ananthakrishnan, Palaniswamy, Florida Atlantic University, Lin, Newman K.
 Abstract/Description

The hydrodynamic interactions between ships in confined waters, restricted in width and depth, is analysed using a numerical surface singularity method called the Panel method. Based on potential flow and rigid free surface assumptions, a source distribution is utilized over the boundary surfaces to model the flow. The strength of the source distribution is obtained on satisfying the normal kinematic boundary conditions, i.e. as a solution of an integral equation. Discretization of the...
Show moreThe hydrodynamic interactions between ships in confined waters, restricted in width and depth, is analysed using a numerical surface singularity method called the Panel method. Based on potential flow and rigid free surface assumptions, a source distribution is utilized over the boundary surfaces to model the flow. The strength of the source distribution is obtained on satisfying the normal kinematic boundary conditions, i.e. as a solution of an integral equation. Discretization of the boundary surfaces yields a system of linear algebraic equations corresponding to the boundary integral equation, which then is solved numerically. From the singularity distribution, the velocity components, pressure coefficients and finally the interaction loads are calculated.
Show less  Date Issued
 1985
 PURL
 http://purl.flvc.org/fcla/dt/14272
 Subject Headings
 ShipsHydrodynamics
 Format
 Document (PDF)
 Title
 Numerical simulation tool for moored marine hydrokinetic turbines.
 Creator
 Hacker, Basil L., Ananthakrishnan, Palaniswamy, VanZwieten, James H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The research presented in this thesis utilizes Blade Element Momentum (BEM) theory with a dynamic wake model to customize the OrcaFlex numeric simulation platform in order to allow modeling of moored Ocean Current Turbines (OCTs). This work merges the advanced cable modeling tools available within OrcaFlex with well documented BEM rotor modeling approach creating a combined tool that was not previously available for predicting the performance of moored ocean current turbines. This tool allows...
Show moreThe research presented in this thesis utilizes Blade Element Momentum (BEM) theory with a dynamic wake model to customize the OrcaFlex numeric simulation platform in order to allow modeling of moored Ocean Current Turbines (OCTs). This work merges the advanced cable modeling tools available within OrcaFlex with well documented BEM rotor modeling approach creating a combined tool that was not previously available for predicting the performance of moored ocean current turbines. This tool allows ocean current turbine developers to predict and optimize the performance of their devices and mooring systems before deploying these systems at sea. The BEM rotor model was written in C++ to create a backend tool that is fed continuously updated data on the OCT’s orientation and velocities as the simulation is running. The custom designed code was written specifically so that it could operate within the OrcaFlex environment. An approach for numerically modeling the entire OCT system is presented, which accounts for the additional degree of freedom (rotor rotational velocity) that is not accounted for in the OrcaFlex equations of motion. The properties of the numerically modeled OCT were then set to match those of a previously numerically modeled Southeast National Marine Renewable Energy Center (SNMREC) OCT system and comparisons were made. Evaluated conditions include: uniform axial and off axis currents, as well as axial and off axis wave fields. For comparison purposes these conditions were applied to a geodetically fixed rotor, showing nearly identical results for the steady conditions but varied, in most cases still acceptable accuracy, for the wave environment. Finally, this entire moored OCT system was evaluated in a dynamic environment to help quantify the expected behavioral response of SNMREC’s turbine under uniform current.
Show less  Date Issued
 2013
 PURL
 http://purl.flvc.org/fau/fd/FA0004024
 Subject Headings
 Fluid dynamics, Hydrodynamics  Research, Marine turbines  Mathematical models, Ocean wave power, Structural dynamics
 Format
 Document (PDF)
 Title
 caHydrodynamic analysis of flapping foils for the propulsion of near surface under water vehicles using the panel method.
 Creator
 Bustos, Julia, Ananthakrishnan, Palaniswamy, Dhanak, Manhar R., Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This thesis presents twodimensional hydrodynamic analysis of flapping foils for the propulsion of underwater vehicles using a sourcevortex panel. Using a simulation program developed in MatLab, the hydrodynamic forces (such as the lift and the drag) as well as the propulsion thrust and efficiency are computed with this method. The assumptions made in the analysis are that the flow around a hydrofoil is twodimensional, incompressible and inviscid. The analysis is first considered for the...
Show moreThis thesis presents twodimensional hydrodynamic analysis of flapping foils for the propulsion of underwater vehicles using a sourcevortex panel. Using a simulation program developed in MatLab, the hydrodynamic forces (such as the lift and the drag) as well as the propulsion thrust and efficiency are computed with this method. The assumptions made in the analysis are that the flow around a hydrofoil is twodimensional, incompressible and inviscid. The analysis is first considered for the case of a deeply submerged hydrofoil followed by the case where it is located in shallow water depth or near the free surface. In the second case, the presence of the free surface and wave effects are taken into account, specifically at high and low frequencies and small and large amplitudes of flapping. The objective is to determine the thrust and efficiency of the flapping –foils under the influence of added effects of the free surface. Results show that the freesurface can significantly affect the foil performance by increasing the efficiency particularly at high Frequencies.
Show less  Date Issued
 2015
 PURL
 http://purl.flvc.org/fau/fd/FA00004351, http://purl.flvc.org/fau/fd/FA00004351
 Subject Headings
 Aerodynamics  Mathematical models, Fluid mechanics, Naval architecture, Ships  Aerodynamics, Steering gear
 Format
 Document (PDF)
 Title
 Hydrodynamic analysis of underwater bodies for efficient station keeping in shallow waters with surface waves.
 Creator
 Bradley, Matthew, Ananthakrishnan, Palaniswamy, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

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

A threedimensional nonlinear timedependent boundaryintegral algorithm is developed to compute wave forces on an underwater vehicle. The effect of viscosity is neglected and the cases for which the effects could be important are discussed. The present algorithm is however an efficient tool to determine wave forces on a submerged body and can also be integrated into a viscous flow algorithm. A numerical wave tank is constructed for the simulation. A damping layer is introduced to minimize...
Show moreA threedimensional nonlinear timedependent boundaryintegral algorithm is developed to compute wave forces on an underwater vehicle. The effect of viscosity is neglected and the cases for which the effects could be important are discussed. The present algorithm is however an efficient tool to determine wave forces on a submerged body and can also be integrated into a viscous flow algorithm. A numerical wave tank is constructed for the simulation. A damping layer is introduced to minimize spurious reflection of scattered waves at the open boundary. A sinusoidal progressive pressure patch is used to generate incident waves. Wave forces are determined using four different methods: viz., (1) FroudeKrylov volume integration method, (2) FroudeKrylov surface pressure integration method, (3) Linear diffraction analysis and (4) Nonlinear diffraction analysis for a range of parameters including incident wavelength and wave height. Results are compared to quantify effects of nonlinearity and diffraction effect of the body.
Show less  Date Issued
 2003
 PURL
 http://purl.flvc.org/fcla/dt/13048
 Subject Headings
 WavesDiffraction, Boundary element methods, Hydrodynamics, Surface waves (Oceanography)
 Format
 Document (PDF)
 Title
 Dynamic analysis of single and multimodule 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 multimodule floating platforms to surface waves is investigated theoretically. Wave exciting forces are computed using methods based on the Morrison equation and FroudeKrylov 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 onemodule platform and hingeconnected twomodule platform are determined by integrating the...
Show moreThe response of single and multimodule floating platforms to surface waves is investigated theoretically. Wave exciting forces are computed using methods based on the Morrison equation and FroudeKrylov 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 onemodule platform and hingeconnected twomodule platform are determined by integrating the corresponding equations of rigidbody 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 rigidbody 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.
Show less  Date Issued
 2006
 PURL
 http://purl.flvc.org/fcla/dt/13399
 Subject Headings
 Ocean engineering, Wave motion, Theory of, Water wavesMathematical models, Drilling platforms, Extreme value theory
 Format
 Document (PDF)
 Title
 Hydrodynamic analysis of an underwater body including freesurface effects.
 Creator
 Puaut, Christophe., Florida Atlantic University, Ananthakrishnan, Palaniswamy, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Boundary integral algorithms are developed to analyze threedimensional inviscid fluidbody interactions, including the nonlinear freesurface effects. Hydrodynamic coefficients are computed for various body geometries, some corresponding to that of small underwater vehicles, in deep waters and near the free surface. The fully nonlinear unsteady waveradiation problem corresponding to forced submergedbody oscillations and forward translation are solved using the mixed EulerianLagrangian...
Show moreBoundary integral algorithms are developed to analyze threedimensional inviscid fluidbody interactions, including the nonlinear freesurface effects. Hydrodynamic coefficients are computed for various body geometries, some corresponding to that of small underwater vehicles, in deep waters and near the free surface. The fully nonlinear unsteady waveradiation problem corresponding to forced submergedbody oscillations and forward translation are solved using the mixed EulerianLagrangian formulation (LonguetHiggins and Cokelet, 1976). By implementing the leadingorder freesurface conditions on the calm surface, linear timedomain solutions are also obtained. The nonlinear and linear results are compared to quantify the nonlinear freesurface effects. Linear frequencydomain analysis of the wavebody interactions is also carried out using a boundaryintegral method based on the simplesource distribution (Yeung, 1974). The linear timedomain and the latter frequencydomain results are also compared for a validation of the algorithms.
Show less  Date Issued
 2001
 PURL
 http://purl.flvc.org/fcla/dt/12845
 Subject Headings
 Boundary element methods, Oceanographic submersibles, Hydrodynamics
 Format
 Document (PDF)
 Title
 Computation of hydrodynamic coefficients and determination of dynamic stability characteristics of an underwater vehicle including free surface effects.
 Creator
 Saout, Olivier., Florida Atlantic University, Ananthakrishnan, Palaniswamy, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The inviscid hydrodynamic coefficients of an underwater vehicle (Ocean EXplorer), including the nonlinear effects of the wave surface, are computed using a boundaryintegral method. A mixed EulerianLagrangian formulation (LonguetHiggins and Cokelet, 1976) is used for the treatment of nonlinear freesurface conditions. The algorithm is validated using the workenergy theorem (Yeung, 1982) and experimental data. Results, in the form of freesurface elevations and hydrodynamic coefficients,...
Show moreThe inviscid hydrodynamic coefficients of an underwater vehicle (Ocean EXplorer), including the nonlinear effects of the wave surface, are computed using a boundaryintegral method. A mixed EulerianLagrangian formulation (LonguetHiggins and Cokelet, 1976) is used for the treatment of nonlinear freesurface conditions. The algorithm is validated using the workenergy theorem (Yeung, 1982) and experimental data. Results, in the form of freesurface elevations and hydrodynamic coefficients, are obtained for a range of body geometries and maneuvers. The openloop dynamics of underwater vehicles are then investigated by solving the 3DOF rigidbody equations of motion (OXY plane). The advantages and possible usage of the developed methodology for the design and control of underwater vehicles, as well as topics for further research, are addressed in the conclusion chapter of the thesis.
Show less  Date Issued
 2003
 PURL
 http://purl.flvc.org/fcla/dt/12981
 Subject Headings
 Hydrodynamics, Oceanographic submersibles, Water waves
 Format
 Document (PDF)