Influence of wave directional spreading of short-crested irregular waves on ship motions and wave loads

Abstract

The conventional ship seakeeping analysis are conducted under the assumption of uni-directional regular or irregular waves. However, full-scale real ships operate in sea states of three-dimensional multi-directional irregular waves. This paper simulates ship motions and load responses in short-crested irregular waves with various directional functions by using CFD-FEM method. First, the simulated waves with various directional functions are comparatively analyzed and validated. Then, ship motions and loads in different short-crested wave states and also in long-crested waves are comprehensively analyzed and compared from the aspect of time series, frequency spectra, statistical values and exceedance of probability. The effect of directional function of short-crested waves on ship motions and loads is comprehensively discussed, which provides useful regression formula for the rapid extrapolation and estimation of ship motions and loads in short-crested waves using the long-crested wave response results. This paper sheds light on the effect of wave directional spreading on ship motions and load responses.