Nonlinear bending moments of an ultra large container ship in extreme waves based on a segmented model test. (1st January 2022) - Tang, Ying
Abstract: The paper presents an experimental investigation on the nonlinear bending moments of an ultra large container ship over 300 m long in rough waves. The design and calibration procedure of the scaled segmented ship model with variable cross-section backbone beam is introduced. Transfer functions of vertical bending moments at different Froude numbers, wave headings and wave heights are analyzed. Ship responses in harsh waves are analyzed and the largest wave height to wavelength ratio exceeds 1/10. It is interesting and significant to analyze the strongly nonlinear behaviors of the ship in such high waves. The resonance frequencies, proportion of high-order harmonic components, asymmetry of hogging and sagging moments as well as the phase differences between wave-frequency and high-order harmonics in extreme waves are investigated systematically. Highlights: Springing in oblique waves is observed and analyzed when wave periods are close to natural period of roll. Strongly nonlinear phenomena like slamming, green water, water entry and exit are observed from image records. Up to 11th-order harmonic bending moments are presented in the amplitude spectrum. Asymmetry of hogging and sagging moments and its causes are investigated. The proportion and phase differences of wave-frequency and high-order components in extreme waves are discussed.