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A higher-order panel method for large-amplitude simulations of bodies in waves

IP.com Disclosure Number: IPCOM000128062D
Original Publication Date: 1999-Dec-31
Included in the Prior Art Database: 2005-Sep-14
Document File: 8 page(s) / 29K

Publishing Venue

Software Patent Institute

Related People

Danmeier, Donald Gregory: AUTHOR [+3]

Related Documents

http://theses.mit.edu:80/Dienst/UI/2.0/Describe/0018.mit.theses/1999-119: URL

Abstract

In this thesis, we simulate large-amplitude motion of threedimensional bodies in waves using a higher-order boundary element method. A `geometry-independent' approach is adopted in which the representation of the body surface is separated from the discretization of the hydrodynamic solution, Traditional formulations of the wave-body problem assume smallamplitude waves and body motions, and perturbation expansion about the mean position of the body and free surface leads to a completely linearized system. In the present thesis, the body boundary condition is imposed exactly, but disturbances at the free-surface are assumed to be small enough to justify linearization. Previous applications of this so-called bodyexact problem have concentrated on the analysis of heave and pitch motion of ships with forward speed. This study focuses on marine applications where a large-amplitude response is induced by small-amplitude incident waves. The time-varying nature of the body-exact formulation makes its numerical solution computationally intensive. Therefore, a new 'higher-order' panel method has been developed to overcome inefficiencies associated with the conventional constantstrength planar-panel approach. Unlike most higher-order schemes, the present method separates the discretization of the hydrodynamic solution from the representation of the body surface by applying a B-spline description of the potential over a generic parameterization of the geometry. This allows for accurate (or even analytic) representation of the surface while retaining the desirable characteristics of higher-order methods, most notably improved efficiency and the ability to evaluate gradients of the potential needed for nonlinear analyses. Robustness and efficiency of the present method are demonstrated by its application to three problems in which the largeamplitude response of the body is important, In the First example, we examine the hydrodynamic loads on an underwater vehicle during a nearsurface maneuver, The vertical drift force is found by integrating the quadratic Bernoulli pressure, and its variation with respect to submergence is shown to complicate the control of the vessel. Next, multi-body interactions are examined in the context of the drift motion of a floating body in the vicinity of a fixed structure. Here, the presence of the structure is shown to repel the floating body against the direction of incident wave propagation for certain conditions.

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A Higher-Order Panel Method for Large-Amplitude Simulations of Bodies in Waves

by

Donald Gregory Danmeier
B.S., Mechanical & Environmental Engineering, University of California at Santa Barbara.....1991

M.S., Naval Architecture & Offshore Engineering, University of California at Berkeley.....1994
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Hydrodynamics

at the Massachusetts Institute of Technology

February 1999
SIGNATURE OF author: [[signature omitted]]

Department of Ocean Engineering

November 1998
CERTIFIED BY: [[SIGNATURE OMITTED]]
J. Nicholas Newman

Professor Emeritus of Naval Architecture Thesis Supervisor ACCEPTED BY: [[SIGNATURE OMITTED]]
J. Kim Vandiver

Chairman, Department Committee on Graduate Students ARCHIVES MASSACHUSETTS INSTITUTE OF TECHNOLOGY LIBRARIES JUN 21 1999

Massachusetts Institute of Technology Page 1 Dec 31, 1999

Page 2 of 8

A higher-order panel method for large-amplitude simulations of bodies in waves

A Higher-Order Panel Method for Large-Amplitude Simulations of Bodies in Waves

by

Donald Gregory Danmeier

Submitted to the Department of Ocean Engineering on November fi, 1998, in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Hydrodynamics

Abstract

In this thesis, we simulate large-amplitude motion of threedimensional bodies in waves using a higher-order boundary element method. A `geometry-independent' approach is adopted in which the representation of the body surface is separated from the discretization of the hydrodynamic solution,

Traditional formulations of the wave-body problem assume smallamplitude waves and body motions, and perturbation expansion about the mean position of the body and free surface leads to a completely linearized system. In the present thesis, the body boundary condition is imposed exactly, but disturbances at the free-surface are assumed to be small enough to justify linearization. Previous applications of this so-called bodyexact problem have concentrated on the analysis of heave and pitch motion of ships with forward speed. This study focuses on marine applications where a large-amplitude response is induced by small-amplitude incident waves.

The time-varying nature of the body-exact formulation makes its numerical solution computationally intensive. Therefore, a new 'higher-order' panel method has been developed to overcome inefficiencies associated with the conventional constantstrength planar-panel approach. Unlike most higher-order schemes, the present method separates the discretization of the hydrodynamic solution from the representation of the body surface by applying a B-spline description of the potential over a generic parameter...