Research Of Two-phase Flow Characteristics And Motion Stability Of Double M-Hull Ship

M-hull ship is a new kind of high performance ship which is combined with the characteristics of planning craft's navigation feature,multi-body high-speed ship's structure feature,microbubble drag reduction ship's resistance feature and hovercraft's similar static lift feature.In high-speed navigation,its wave-making is much smaller than conventional planning craft because of its unique channel design,thus the wave making resistance is greatly reduced.Due to the water-air mixing phenomenon in the tunnel,it makes the hull wetting and reduces the viscosity coefficient of the medium.The design of steps makes it easier for the craft get into the planning phase.And the dynamic pressure zone in the tunnel further uplift the boat out of the water,so the friction resistance can be decreased.The design of the tunnels makes the hull form a transverse structure similar to that of a multibody ship,so it has good lateral stability.Obviously that the M-hull ship has characteristics of resistance excellent performance and concealment and stability,based on M-hull ship,double M-hull ship is put forward.However,the research on M-hull ship is still mostly limited to the model test method,and resistance and navigation state prediction,while the study on the mechanism of drag reduction,flow field details and force characteristics is hard to carry on and the model test is time-consuming and laborious.Therefore CFD method based on RANS numerical tank is unique choice of research tools.However,there are still many problems to be solved in the numerical simulation of M-hull ship due to its high-speed navigation characteristics,violent changes of navigation state,the characteristics of the water-gas mixed flow field and the complex force characteristics.Therefore,this research is carried out based on the viscous CFD method and the overset grid technique in the commercial software STAR-CCM+ platform.And research on two-phase characteristics and motion stability of double M-hull ship is proposed,the resistance prediction is performed based on the numerical simulations of double M-hull ship's 2-DOF motion of direct navigation in calm water,and the realtime capture is realized to solve the dynamic navigation problems.The main research contents include:(1)The calculation results of different grid schemes are compared with the model test for verification and validation,then the optimal mesh scheme for numerical simulations of the direct navigation in calm water for double M-hull ship is determined.(2)Using the grid schemes for the numerical simulations with different working conditions of double M-hull ship(different displacement and longitudinal position of gravity center)and series of double M-hull ship are simulated and compared with experimental results for further verification and validation.(3)Research that the influence on the direct navigation performance by different steps is carried on based on numerical simulation.(4)The longitudinal motion stability performance(porpoising phenomenon and jump motion phenomenon),seakeeping and direct navigation performance in calm water for both single and double M-hull ships are studied.In summary,based on the numerical wave tank,the optimal scheme for numerical simulation of the double M-hull ship is proposed,and is validated by various grid schemes,various working conditions and series kinds of ships.The comparative study is performed on double M-hull ships with different steps.And the performance of seakeeping and stability are also discussed.Above all,this paper can provide a certain reference value for the research and design of double M-hull ship and also the numerical simulation.