Time-Domain Simulation of Nonlinear Ship Motions and Wave Loads

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Authors
  1. Ando, S.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN)
Abstract
In the assessment of the ability of a ship structure to withstand specified sea environments with an acceptable risk of failure, accurately predicted loads are vital. Of paramount importance are extreme loads on the hull structure, which usually occur when a ship undergoes large heaving and pitching motions in rough seas, sometimes accompanied by impacts between the bow and waves. In such severe motions, the instantaneous wetted part of the hull varies considerably, and linear theory's basic assumption of small-amplitude waves and ship motions is flagrantly violated. Yet it is not possible to treat the geometric nonlinearity of the wetted part of a hull and transient phenomena like slamming adequately in the frequency domain; however, they can be incorporated into time-domain analysis relatively easily. It is generally believed, therefore, that practical calculations of combined wave-induced and slamming forces may only be carried out in the time domain. This paper describes the application of strip theory to time-domain calculations of nonlinear ship motions and hull-girder loads in head seas. In this approach, the differential equations of ship motion are solved numerically by calculating hydrodynamic forces and coefficients at each time step by strip theory, taking into account nonlinearities relating to large relative motion between waves and the ship hull. TRUNCATED
Keywords
Time domain;Head waves;Irregular waves;Nonlinear theory;Wave loads;VBM (Vertical Bending Moments)
Report Number
DREA-SL-1999-075 — Paper
Date of publication
09 Jul 1999
Number of Pages
10
DSTKIM No
CA000071
CANDIS No
511557
Format(s):
Hardcopy;Document Image stored on Optical Disk

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