Numerical Study On Green Water And Bow Flare Effect For Ship Advancing In Waves

Green water is a phenomenon which vessels encounter wave, and at the same time liquid surpasses freeboard and flush onto deck. When it happens, the green water could damage equipments, cargos and superstructures on the deck, and even be able to capsize the ship under severe circumstance. The green water phenomenon has long been noticed by researchers and engineers of naval architecture and ocean engineering, but it is one of the strongly nonlinear ship-wave interaction problems which is difficult to be solved mathematically, and the physical phenomenon of the occurrence of green water is very complicated. Traditional theory and numerical research could only descript the green water process to some limited extent, and couldn't explain the mechanism of it, so it was difficult to solve practical problems. Now with the rapid development of computation technology, numerical simulation has become an important method to deal with green water problem, and by combining the advantages of numerical methods and existing theory, it would be possible to solve engineering problems practically and effectively.On the basis of reviewing and summarizing the development and research process of green water problem, the work in the following aspect has been carried out:Firstly, by taking advantages of the virtues of both potential flow theory and CFD technique, a convenient numerical method to simulate green water on deck is outlined. Aiming at engineering application, a moving foredeck model to simulate of green water phenomenon has been established, and then the 3-D numerical simulation of green water occur on the deck of S175 model is carried out. The method of the simulation is based on the second development of commercial software Fluent. By using dynamic mesh to consider the movement of ships, the green water flow and impact on deck and structure of S175 moving in head sea are numerically simulated and analyzed, and the results agree well with the corresponding experimental ones. The mesh number in the simulation case by using present method is relatively small and the computing process is more efficient, which indicates this approach is a practical way to optimize bow shapes.Secondly, based on the numerical method, the effect of bow flare in the green water problem is discussed under different conditions by changing bow flare of the ships. Through the simulation of the green water flow and impact of the structure on deck under different working conditions, it shows the effectiveness and convenience of this method to deal with green water problems.Results indicate that present method could simulate the green water process of the ships accurately, and it can practically solve engineering problems with effectiveness. At the same time, the method can be used in analysis different factors which influence the green water phenomenon of the ships, and can be applied to the further research of green water problem.