A numerical study on local characteristics of predetermined irregular wave trains |
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| Authors: | Xiufeng Liang Jianmin Yang Jun Li |
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| Institution: | a State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai 200030, China
b Shanghai Waigaoqiao Shipbuilding Co., LTD., Shanghai, China |
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| Abstract: | In actual sea states, damage to offshore floating structures is usually caused by a few extreme waves or wave groups in an irregular wave train. Accurate simulation of the irregular wave trains can lay a solid foundation for understanding the local flow field and impact loads that would potentially cause such damage. This paper describes how the generation of a single extreme wave was investigated. Determination of the wave-maker motion for generating specified irregular wave trains is the key to this work. First, an experimental irregular wave train was decomposed into a certain number of small-amplitude waves. Fourier series expansion was performed to determine the amplitude and the initial phase angle of each wave component. Then a hydrodynamic transfer function was used to calculate the amplitude of the wave-maker motion associated with each wave component. Superposition was made on all the wave components to get the final wave-maker motion. During the numerical simulation, calculated horizontal velocity profiles of the extreme wave at different moments were analyzed and compared with experimental results, and a satisfactory agreement was obtained. In the simulation, VOF method was employed to capture the free surface, and a dissipation zone was used to deal with wave reflection. |
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| Keywords: | Numerical wave tank Irregular wave train VOF Dynamic mesh Horizontal velocity profile |
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