2.5D Computational Method For Ship Motions And Wave Loads Of High Speed Ships

The development of suitable numerical techniques of ship motions and wave -induced loads of high speed vessels is important for the prediction of seakeeping and structural design of high performance ships. In recent years the high speed slender body theory or 2.5D theory was developed especially for ship motions and wave loads prediction of fast displacement ships. The formulation of 2.5D theory contains most important forward speed effects on the free surface for the hydrodynamic calculation of fast ships; At the same time, the solution is based on two dimensional Laplace equation according to the slender body assumption, the computational effort of 2.5D theory is much less than that based on three dimensional Green's function with forward speed.In this paper, the two dimensional transient free-surface Green's function is used to solve the formulation based on 2.5D potential theory. The hydrodynamic coefficients, ship motions and wave-induced loads responses are calculated and are compared with model test data and S.T.F. strip theory. The aim of this thesis is to investigate the applicability of this theory for hydrodynamic prediction of fast ship and promote it for engineering application. The major work is as follows:1.Using two dimensional transient free-surface Green's function, an time marching integral equation on the body surface is developed to solve 2.5D potential theory. Ship motions and wave induced loads of fast monohulls and catamarans in oblique waves are calculated. A stable numerical algorithm is presented to calculate the hydrodynamic coefficients by numerical comparisons and analysis which can avoid the error from numerical difference about the fluid potential. The effect of hydrodynamic interactions between demihulls of catamaran on ship motions is investigated.2. The linear hydroelastic analysis of wave induced loads for high speed catamarans are solved by 2.5D potential theory based on source distributed integral equation. The three dimensional FEM and modal analysis method are used to calculate the hydroelastic responses of ship motions and sectional loads of catamarans. According to the slender structural characteristics of demihulls, the simplified representation of mode shapes is introduced and the generalized hydrodynamics are calculated by this simplified mode shapes. The hydroelastic...