EQUATIONS FOR NON-QUASI STEADY SHIP MOTIONS

Quasi-steady techniques in general use for the prediction of ship manoeuvres as referred to in Recommendation 6.4 of the Proceedings of the 13th ITTC (1972) 1484 are not applicable in cases where the spectra of the forces acting are broad band as e.g. in collisions. Adequate models for the description on non-linear ship dynamics including memory effects are functional polynamials, in the linear case Duhamel integrals. As has been pointed out previously this behaviouristic description in the time domain is hardly practical for simulation purposes even with very large computers. Much more simple are equivalent state space descriptions as is well known in many other fields but apparently not yet in our profession. An account of the general theory, of the linear theory, and application to hydrodynamic systems has recently been published and an application to the collisiions of ships is presented. The hydrodynamic damping and mass of the simple model are compared with theoretical data for a scale model of the Japanese nuclear ship Mutsu. For most applications the simple model will apparently be sufficient, and if it is not, the description may be improved by introduction of further fluid states, maybe two or four. Consequently the step responses as simulated and observed for the same scale model are quite close. The example given is only the simplest application of the theory of state space models. Non-linear models will have to be developed for multidimensional situations not only in ship dynamics in studying state space models was primarily the need for an adequate tool for investigation and design of marine traffic control systems for congested waters.

  • Supplemental Notes:
    • Presented at the 14th International Towing Tank Conference, 1975.
  • Corporate Authors:

    National Research Council of Canada

    1200 Montreal Road
    Ottawa, Ontario  Canada  K1A 0R6
  • Authors:
    • Schmiechen, M
  • Publication Date: 1975

Media Info

  • Pagination: n.p.

Subject/Index Terms

Filing Info

  • Accession Number: 00323693
  • Record Type: Publication
  • Source Agency: Stevens Institute of Technology
  • Files: TRIS
  • Created Date: May 21 1981 12:00AM