Time domain prediction of seakeeping behaviour of catamarans

Abstract

The numerical predictions of the seakeeping characteristics of catamarans with and without forward speed are presented using a direct time domain approximation. Boundary-Integral Equation Method (BIEM) with three-dimensional transient free surface Green function and Neumman–Kelvin linearization is used for the solution of the hydrodynamic interactions in the gap between catamaran hulls and solved as impulsive velocity potential. The numerical results have shown that the response of the fluid between multi-hulls can affect seakeeping performance and influence the hydrodynamic forces and the motion amplitude operators of the floating multi-bodies. It is also shown numerically if the critical reduced frequency is smaller than the ratio of vessel length to hull separation, the wave interactions between hulls are very significant due to trapped waves in the gap of twin-hull. A hemi-spheroid catamaran, Wigley catamaran, and DUT high speed catamaran hull forms are used for the numerical analyses and the comparisons of the present ITU-WAVE numerical results for added-mass, damping coefficients, exciting force, and response amplitude operators show satisfactory agreement with existing numerical and experimental results.