A method for hydroelastic analysis of high speed monohulls and catamarans, subjected to continuous wave loads, is presented. The flexibility of the vessel is taken into account by using a number of eigenmodes, in addition to the six rigid body modes, as generalized degrees of freedom. These eigenmodes are obtained from a free vibration analysis of the "dry" structure; based on a finite element formulation. The fluid forces are calculate by generalizing eh linear 21/2-dimensional method of Faltinsen and Zhao, so that the additional modes can be included. The 21/2-dimensional formulation is computationally efficient, and it incorporates the important wave systems that are generated by high speed vessels. Theoretical predictions are compared with experimental results for a flexible catamaran model in regular and irregular long crested waves. Head, bow and beam seas are studies. Vertical shear forces and vertical bending moments in the hulls and the cross structure, in addition to heave, pitch and roll motions, are investigated. The comparisons indicate that a modal approach is well suited for the prediction of wave-induced structural responses in high speed vessels. Both quasi-static responses and resonant vibrations (springing) were generally quite well predicted by the theory. Resonant heave and pitch motions however, were overpredicted. The disturbance of the steady flow around the ship is neglected in the unsteady problem, and this seems to be an important reason for these overpredictions. Some discrepancies may also have occurred due to hydrodynamic interactions between the two hulls and three-dimensional effects at the stern; two other phenomena that are not included in the theory. The experiments demonstrate that the structural response may be nonlinear even if the ship motions behave linearly.

  • Supplemental Notes:
    • Norges Tekniske H gskole, Trondheim, Norway, MTA rpt 1995:109 [153 p, 129 ref, 9 tab, 69 fig]
  • Authors:
    • Hermundstad, O A
  • Publication Date: 1995


  • English

Subject/Index Terms

Filing Info

  • Accession Number: 00728052
  • Record Type: Publication
  • Source Agency: British Maritime Technology
  • Files: TRIS
  • Created Date: Nov 4 1996 12:00AM