甲板上浪和冲击载荷的数值模拟

Numerical Simulations for Green Water Running on Deck and Impact Loads1
Lin Zhaowei, Zhu Renchuan, Miao Guoping
School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University Shanghai, P.R.China (200030)
E-mail：gpmiao@
Abstract A technique of dynamic mesh is specially introduced in a 2-D numerical wave tank to simulate the green water incident on a fixed FPSO model in head waves and oscillating vessels in beam sea conditions, respectively. Numerical results agree well with the corresponding experimental ones. It indicates the present numerical scheme and method can be used to actually simulate the phenomenon of green water on deck, and to predict and analyze the impact forces on floating structures due to green water. It is of great significance to further guide the ship design and optimization, especially for ship bow and its strength design. The mechanism may also help seaman to impose operation restrictions to avoid severe green water incidents. Keywords: Green water， numerical wave tank， dynamic mesh.
1 Introduction
Green water is one of the strongly nonlinear ship-wave interaction problems, usually occurring in harsh sea environments when an incoming wave significantly exceeds the freeboard and water runs onto the deck. Damage of deck equipments and superstructures, and deck cargo shifting will probably be caused by the huge impact forces due to the severe green water incidents. Ship capsizing may even happen due to green water on deck for high speed vessels. For running ships, green water incidents may be avoided by taking some operation measures, such as reducing the advancing speed or altering the course. For the ocean structures, such as FPSO (Floating Production, Storage and Offloading Unit), moored in a specified sea area, however, no operation measure could be adopted to reduce the possible green water on deck, and risks resulted from green water will be even severer than other vessels. Recently, some cases of bow damage and superstructures destroy of FPSO caused by server green water incidents were reported (Mac Gregor, 1999). The green water problem is arousing more attentions for research. In the past, the research of green water problem was mainly relied on the experimental means. Some limited progresses were also achieved recently with the development of numerical techniques and methods. Traditionally, probability method, combined with hydrodynamic theory, was adopted to estimate and analyze the green water related problems. The method cannot predict the amount of water and the hydrodynamic load on decks when water runs onto deck but gives only the probability of deck wetness and the pressure distribution on the deck, based on the assumption that the pressure on the deck corresponds to the static water pressure of shipped water. Subsequently, some other theories and methods based on the potential theories were developed to tackle the problem to some extends. For example, the dam breaking theory and wave overtopping theory were used to simulate the deck flow (Buchner, 1995；Greco et al, 2000), the flooded water theory and shallow water wave theory were applied to simulate the water running on deck (Mizoguchi，1989; Huang，1995; Ogawa et al，1998). Mixed Euler-Lagrange method was also adopted for parametric research for green water incident (Buchner & Cozinijn，1997；Faltinsen et al，2002). The
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Support by the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No.20030248014)
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