TIME DOMAIN PROGRAM OF SHIP MOTIONS AND SEA LOADS IN IRREGULAR HEAD SEAS

Authors
  1. Johnston, G.W.
  2. Foster, S.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN);Aerospace Engineering and Research Consultants Ltd, Downsview ONT (CAN)
Abstract
A prediction method and an associated computer code have been developed to solve the linear time domain hydrodynamic problem in six degrees of freedom and to predict hull motions in three degrees of freedom for the longitudinal modes. Following established practice, the potential flow formulation is linearly decomposed into independent radiation and diffraction problems. While the focus of the study has been the fully linear three-dimensional problem, certain nonlinear aspects have been addressed. Accordingly, the nonlinear hydrostatic and Froude-Krylov forces are determined by integration of the corresponding pressure fields over the instantaneous wetted hull surface using an algorithm which automatically generates hull panels up to the instantaneous waterline. For the diffraction problem, only incident waves from beam to head seas are supported. The methodology is applicable to completely submerged and surface piercing hulls at both zero and forward speed conditions. For surface piercing bodies, however, the behaviour of the wave part of the Green function near the free surface poses significant difficulties. Manifest as divergent oscillations in the potential solutions, these difficulties are associated with terms corresponding to the waterline and panels adjacent to it. These problems have only been partially addressed.
Keywords
Surge;Froude-Krylov;Panel methods;Head seas;Free surface
Report Number
DREA-CR-93-464 — Contractor Report (Final)
Date of publication
01 Sep 1993
Number of Pages
164
DSTKIM No
94-03131
CANDIS No
141194
Format(s):
Hardcopy;Originator's fiche received by DSIS

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