The Numerical Investigation Of Mechanics Characteristic And Motion Response On Maneuvering Of The Trimaran Planing Hull

As the promulgation of the IMO Manipulation Failure Equity,the ship manipulation performance has attracted much more attention.And the planing trimaran hull is essential as a part of the high-performance hull due to the excellent performance in resistance and stability,which also made it as a key research in ship model between various countries.However,the public data relevant to the manipulation characteristic is rarely due to the lack of research.Considering the particularity of the hull type,with the increasing of the speed,the performance and mechanism of a trimaran planing hull maneuverability in the waves are quite different from the conventional displacement ships and even from the ordinary planing hull.During the process of maneuvering,the air-liquid mixed flow in each side of the tunnel is asymmetry and nonlinearity.Especially when taking the wave force influence into account,the attitude change is much more obvious.The attitude affects the manoeuvring force and motion response characteristics directly.Appropriate tumble is conducive and acceptable in turning performance,While a large attitude change means that the instability such as surf-riding and broaching.The paper focused on the planing trimaran,studied the force and motion response characteristics in calm water and regular wave by using the mathematical model simulation method(the Ship Manoeuvring Mathematical Model Group,MMG),while the dynamic lift and surface propeller propulsive force and steering force are considered.Also as a comparison,the computational fluid dynamics(CFD)method based on overlap mesh technology is adopted to verified the results,the phenomena appearing in straight and curve movement have been analyzed and investigated.As a conclusion,the MMG method is focused on the qualitative scope analysis,while the CFD method adept at descripting the phenomena of the flow field and the force acting mechanism during manoeuvring process.And the paper is arranged as following.Firstly,the resistance and maneuverability of the planing trimaran hull are verified and studied by model test in towing tank and real hull sea trial.From the point of the straight motion,considering the characteristics of the resistance curve with the double resistance peaks,the relationship between surface propeller trim angle with the velocity of the trimaran planing hull is studied.By comparing the maneuverability test results with the dimensionless trajectories of the monohull planing hull and conventional displacement hull,the planing trimaran shows a better flexibility and maneuverability.The experimental results not only provide effective data for the analysis of planing trimaran in running state that changed from displacement state to the planing state,but also the turning ability during high speed as well as the quantitative verification and calculation method are studied.Secondly,the dynamic equations of the planing trimaran in calm water are established,while the dynamic lift is taken into account,and then the maneuverability in calm water is studied by the method based on the MMG mathematical simulation.Considering the characteristics of the trimaran planing hull,the mathematical models of dynamic lift,surface propeller thrust and steering force are presented.The horizontal plane constraint motion is extended to the vertical plane,the component of the vertical surface is considered when calculating the viscosity and inertial force hydraulic dynamic coefficient.The maneuverability of the trimaran planing hull in displacement,semi-planing and planing state were analyzed,while the simulation results and the reliability of the mathematical model are investigated by compared with the test and sea trial result.Thirdly,the numerical simulation of CFD is used,that is based on oversets grids and volume force method to verify the maneuverability of the planing trimaran hull in calm water.The straight motion hydrodynamic mechanism of the hull in calm water and regular waves are studied by resolution of the various forces and motion behaviors.The characteristics of hydrodynamic and aerodynamic in tunnel are observed during the turning period,and the role of the tunnel is summarized.And based on that,the maneuverability of the planing trimaran in regular waves and calm water are investigated.With the CFD numerical simulation method,the turning motion with the encounter frequency in the three states is calculated,and the nondimensional hydrodynamic coefficients and the wave force database are suppled.The maneuverability of the planing trimaran hull is verified by comparing with mathematical model simulation method.Further,the reliability of the method is verified.Finally,the instability of the planing trimaran hull in waves is studied,the motion details were captured and studied by CFD simulation,and the instability of the planing trimaran is divided into two categories:The instability caused by frequent steering and the position in waves.The formation mechanism of the two instability types is explained by phenomenon analysis.By analyzing the position,attitude and motion response in surf-riding,the safe steering range is given through the joint use of the two maneuverability prediction methods,which provides an engineering basis for studying the maneuverability of the planing trimaran hull.