Current Search: Boundary element methods (x)
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 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
 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
 Design approaches for asymmetrical marine pipeline cathodic protection systems.
 Creator
 Qian, Haijun., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Marine pipeline cathodic protection systems for asymmetrical situation were systematically investigated by means of a newly proposed approach and Boundary Element Method (BEM). Potential attenuation profiles from BEM modeling indicate that farfield cathode potentials of different pipe sections approach identical values under different coating resistance and different electrolyte resistivity conditions provided anodes are separated by at least 10m and metallic resistance is negligible. A...
Show moreMarine pipeline cathodic protection systems for asymmetrical situation were systematically investigated by means of a newly proposed approach and Boundary Element Method (BEM). Potential attenuation profiles from BEM modeling indicate that farfield cathode potentials of different pipe sections approach identical values under different coating resistance and different electrolyte resistivity conditions provided anodes are separated by at least 10m and metallic resistance is negligible. A series of equations based on the Slope Parameter Method (SPM) has been modified for more extensive applicability. Several design examples have been analyzed and the results verified by BEM. Cathode potential and current demands projected by the new method are consistent with those of BEM. The inclusive equation for even anode spacing CP has been modified to include the cable parameters by combining cable resistance and the anode resistance. Current demand for existing pipelines can be determined by either of two methods. The first utilizes the inclusive equation and involves solving this for current demand based upon a known potential profile. The other is based on SPM.
Show less  Date Issued
 2003
 PURL
 http://purl.flvc.org/fcla/dt/13098
 Subject Headings
 Underwater pipelines, PipelinesCathodic protection, Boundary element methods
 Format
 Document (PDF)
 Title
 General relativistic quasilocal angular momentum continuity and the stability of strongly elliptic eigenvalue problems.
 Creator
 Wilder, Shawn M., Beetle, Christopher, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

In general relativity, angular momentum of the gravitational field in some volume bounded by an axially symmetric sphere is welldefined as a boundary integral. The definition relies on the symmetry generating vector field, a Killing field, of the boundary. When no such symmetry exists, one defines angular momentum using an approximate Killing field. Contained in the literature are various approximations that capture certain properties of metric preserving vector fields. We explore the...
Show moreIn general relativity, angular momentum of the gravitational field in some volume bounded by an axially symmetric sphere is welldefined as a boundary integral. The definition relies on the symmetry generating vector field, a Killing field, of the boundary. When no such symmetry exists, one defines angular momentum using an approximate Killing field. Contained in the literature are various approximations that capture certain properties of metric preserving vector fields. We explore the continuity of an angular momentum definition that employs an approximate Killing field that is an eigenvector of a particular secondorder differential operator. We find that the eigenvector varies continuously in Hilbert space under smooth perturbations of a smooth boundary geometry. Furthermore, we find that not only is the approximate Killing field continuous but that the eigenvalue problem which defines it is stable in the sense that all of its eigenvalues and eigenvectors are continuous in Hilbert space. We conclude that the stability follows because the eigenvalue problem is strongly elliptic. Additionally, we provide a practical introduction to the mathematical theory of strongly elliptic operators and generalize the above stability results for a large class of such operators.
Show less  Date Issued
 2014
 PURL
 http://purl.flvc.org/fau/fd/FA00004235
 Subject Headings
 Boundary element methods, Boundary value problems, Differential equations, Elliptic  Numerical solutions, Differential equations, Partial  Numerical solutions, Eigenvalues, Spectral theory (Mathematics)
 Format
 Document (PDF)