TIME-DOMAIN ANALYSIS FOR PREDICTING SHIP MOTIONS

The use of time-domain analysis for predicting ship motions is investigated. In the method, the hydrodynamic problem is solved directly in the time domain as an initial value problem starting from rest rather than the more conventional frequency-domain approach. For linearised problems the time-domain and frequency-domain results are Fourier transforms of one another and are therefore complementary. For fully nonlinear simulations the time-domain approach is preferred. In this paper, both linear and body-nonlinear problems will be discussed. The body-nonlinear problem requires the body boundary condition to be satisfied on the instantaneous position of the body while maintaining the linearised free surface boundary condition. In the linear problem, both the free surface and body boundary conditions are linearised. The body boundary condition is linearised about the mean position of the body. Because the free surface condition is linearised about the calm water level, a time-domain Green function approach is used to solve both problems. Results of linear time-domain calculations are presented for the Wigley hull form and compared with experiments. Body-nonlinear computations are shown for a submerged ellipsoid. In both cases, the influence on the time-domain results of the singularity in the frequency domain at tau=1/4 is discussed.

  • Supplemental Notes:
    • Intl Symposium on the Dynamics of Marine Vehicles and Structures in Waves, 2nd; 24-27 June 1990, Brunel Univ, Uxbridge, U.K. Sponsored by Office of Naval Research (London and Washington D.C.) and RINA. Procs. Publ by Elsevier Science Pubs, ISBN 0-444-89020-3, p 49 [16 p, 32 ref, 13 fig]
  • Authors:
    • Beck, R F
    • Magee, A R
  • Publication Date: 1990

Language

  • English

Subject/Index Terms

Filing Info

  • Accession Number: 00716238
  • Record Type: Publication
  • Source Agency: British Maritime Technology
  • Files: TRIS
  • Created Date: Feb 28 1996 12:00AM