The Longitudinal Motion Of Tumblehome Hull With Speed And Viscous Numerical Simulation Of Green Water

The shape of tumblehome hull below waterline is the convex curve form,the part above waterline inclines inward 10 °-20 °,and the side wall of superstructure inclines inward 7 °-15 °.In high sea conditions,the tumblehome hull prone to encounter green water phenomenon.The water on the deck will not only affect the performance of the equipment on the deck,but also have a considerable impact on the structure of the tumblehome hull.At the same time,the non-linear motion of tumblehome hull caused by green water will lead to the insufficiency of overall stability,and may generate the parametric rolling,in severe cases the green water may also capsize the ship.So in the research of tumblehome hull,great attention should be given to the green water phenomenon.Research on the green water usually uses the method of combining potential flow theory and the viscous flow,the movement of the hull are solved with the method of potential flow theory,and the water on deck uses the viscous flow to simulate.Viscous CFD software is used to simulate real-time movement of speed tumblehome hull in head wave under the environment of pure viscosity,to explore the green water phenomenon of tumblehome hull,especially the "wave run-up" phenomenon.In this paper,the numerical wave tank is first established,it has realized the first order stokes wave,second order stokes wave and five order stokes wave.Then analyzes the wave precision and reliability.Secondly calculating the frequency response function curve of naked tumblehome model and tumblehome model with appendage at different speed in head regular wave;And forecast longitudinal motion of the naked tumblehome model,tumblehome model with appendage and tumblehome model with bulwark at different speed in the regular wave which has different wave steepness,and accurately capture the phenomenon of green water and nonlinear ship motion,based on these,it is convenient to analyzed how the speed of the ship,wave steepness and bulwark influence on green water phenomenon.Finally using the multi-domain coupling method to forecast the influence of water volume on the deck on ship's longitudinal motion.Draws the following conclusions:(1)the longitudinal motion of tumblehome hull in the large steep wave exist obvious nonlinear phenomenon,that is combined action of hull inwardness and green water.(2)The green water of speed tumblehome hull will increase the longitudinal motion of ship,influenced by nonlinear motion,the longitudinal motion of tumblehome hull is bigger than straight wall or flare ship type.(3)The bilge keel,rudder and propeller shaft to reduce amplitude of pitch motion is limited,but it can effectively reduce the amplitude of the heave movement,ease green water phenomenon of tumblehome hull.(4)Viscous CFD method is suitable to explore the nonlinear motion of tumblehome hull.It can accurately capture the complex motion of the water.(5)reducing the speed and the wave steepness can reduce the volume of water on the deck,but unable to effectively reduce the height of " wave run-up",and the closed bulwark,although the water volume can be lower,but as a result of the existence of reflux,does not reduce the total water on the deck,also cannot reduce the height of " wave run-up".(6)Open FOAM can implement multi-domain coupling calculation well,providing an effective means for the viscous numerical simulation of related areas.