Nonlinear Subharmonic Roll Response of a SWATH Ship in Regular Beam Seas

Abstract

One of the primary virtues of a Small Waterplane Area Twin Hull ship is its low motion characteristics in severe seas. By varying the appropriate inertial and geometric parameters, designers can de-tune a SWATH ships' motion responses for a particular expected operating environment. Using model test data and linearly based motion prediction simulations, the effects of various design changes on motions can be studied. The occurrence of subharmonic roll motion has been observed in several past SWATH experiments and is not predicted using linear techniques. This nonlinear response has generally occurred on designs where the natural roll frequency is roughly half of the natural heave frequency. The extent of the boundaries of this stability, has not been well defined for a SWATH ship. This investigation provides experimental results defining the stability boundary for the roll motion of a SWATH drifting in beam seas and to study the possible cause of this phenomenon using a nonlinear math model of the coupled heave roll response.

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Document Details

Document Type
Technical Report
Publication Date
Dec 01, 1989
Accession Number
ADA217253

Entities

People

  • Christopher J. Hart

Tags

DTIC Thesaurus Topics

  • Boundaries
  • Data Acquisition
  • Differential Equations
  • Engineering
  • Equations
  • Frequency
  • Marine Engineering
  • Measurement
  • Metacentric Height
  • Military Research
  • Naval Architecture
  • Resonant Frequency
  • Standing Waves
  • Test Equipment
  • Test Facilities
  • Test Methods
  • Transfer Functions

Readers

  • Control Systems Engineering.
  • Marine Hydrodynamics