In this paper, the focused wave and current interaction with a moored JIP Spar platform are investigated using a time-domain higher order boundary element method (THOBEM). Embodied by a linear superposition of finite cosine waves, the focused wave can be efficiently simulated through adjusting the initial phase of cosine wave and adding corrected wave. The finite element method is used to simulate the distortion and tension of the mooring system. The great effects of current and mean drift forces on the position and amplitude of the focus peak value of hydrodynamic characteristics are investigated.


With the development of offshore oil-gas exploitation, the study of hadal marine zone is an inevitable trend of ocean development. The waves with large wave steepness (e.g., focused wave) always appear in deep sea, resulting in tremendous damages to platforms. Under the combined effects of wave and current, the offsets of floating platform are sometimes measuring dozens of meters. For the sake of safety, extensive experimental and numerical studies were carried out for the solution of the interaction of extreme wave with floating platform in current. In the early period, most researchs about extreme wave were studied by experimental method. Baldock et al (1996) developed a series of researches of extreme waves in finite water depth, nonlinear dynamic characteristics are investigated. A wave basin experiment has been performed to investigate the interactions between multidirectional focused wave and vertical bottom-mounted cylinder by Li et al (2012). A laboratory study of the focusing of transient and directionally spread surface water waves was studied by Johannessen and Swan (2001). However, the extreme wave impact on offshore structures has not been fully understood as the impulsive wave pressure and wave loading on the structures are difficult to predict due to the complexity of the problem.

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