Performance Analysis And Experimental Study Of Ship Anti Rolling Device Based On Magnus Effect

Ship stabilization has gradually become a necessary function of high-performance ships.The ultimate goal of ship anti-rolling device is to achieve economic and practical ship antirolling at all forward speed.This paper applies Magnus effect to design and manufacture speed regulation cylinder.The cylinder,which replaces the fin of fin-stabilizer,can be used in the anti-rolling device to provide lift force with forward speed.On the other hand,the cylinder can generate lift force in the still water by using its own swing,therefore it provides an anti-rolling solution for all speed,especially Zero-speed level.In this paper,the influence of Reynolds number,rotational speed ratio and length-diameter ratio on hydrodynamic performance of rotating cylinder is analyzed by numerical and experimental research.The shock absorption cylinder with circular protuberance is designed according to the wind resistance of the giant cactus.The lifting unit mechanism is designed and processed for the optimized cylinder,and the performance is verified by the tests.The antirolling device of the whole ship is also designed and developed.Eventually,the ship model that carries four lifting units is used in the seakeeping test.Firstly,In this paper,the performance of various rotating cylinders is studied,numerical simulation and experimental method are used to study the hydrodynamic performance of the rotating cylinder with free end.In numerical simulation,LES method is used,and in experiment,a hydrodynamic testing device with a false bottom is developed independently.It is found that the length diameter ratio is positively related to the lift drag ratio of the rotating cylinder,and the effect of the free end of the rotating cylinder on overall lift performance is discussed.The hydrodynamic performance of the rotating cylinder with length-diameter ratio of 5,7 and 9 at high Reynolds number and variable speed ratios is obtained.In order to improve the L/D ratio,a variety of shape structures with length-diameter ratio of 7 are designed.The oscillation of the rotating cylinder is also monitored during the test.A prototype which is based on the giant pillar cactus,uses the bionic round convex structure has an average anti-rolling efficiency of 54.36%and a maximum efficiency of 82.46%.The vorticity field information is obtained by numerical simulation and PIV test respectively.Based on this,the vibration generation process and the mechanism of shock absorption of bionic cylinder are discussed and analyzed.By comparing the rotating cylinder and NACA system hydrofoil,their lift performance are similar under the same flow area,which proves that the rotating cylinder has smaller volume and better retractability.Through the structure and hydrodynamic performance analysis,the suitable shape and aspect ratio of the Magnus lift cylinder is determined.Based on the research of rotating cylinder,the Magnus swing anti roll lifting unit of the electric servo power source and its hydrodynamic matching measuring device is designed and manufactured by using the lift cylinder as a core component.The unit is upgraded by optimizing the moment of inertia and improving the electrical control.To optimize the moment of inertia,the shaft body of the BLDCM is transformed based on the principle that structural strength parts are close to the rotating center axis.At the same time,the low filling water-resistant 3D printing materials which require calculation rigidity is used as the water tight structure.To improve the electrical control,the brake energy storage circuit with the super capacitor as the core is adopted,which reduces the inductive load between the rotating commutators,which enhances the commutation response ability of the swing lift unit.The pool test proves that the swing lift unit can provide continuous lifting force,at the same time,PIV flow field measurement test is used to reveal the flow details.This paper studies the lift difference that uses swing speed,swing speed ratio and swing angle as parameters.It is concluded that the swing angle is positively related to the average lift.The corresponding anti roll control method is proposed for a surface ship equipped with four lifting units.According to the motion form of the lift unit and the roll mode of the ship model,the anti-rolling control is classified into zero speed anti roll,low speed anti roll and beyond critical speed anti roll.The study selects swing anti roll at zero-speed,differential swing anti roll at low speed,and non-swing anti roll at beyond critical speed.Energy-saving control methods are introduced based on prediction of ship motion in waves,such as waiting roll reduction,trigonometric function roll reduction and equal period roll reduction.In order to determine the parameter control of the system to the lift unit,the PID control is adopted,and the anti roll control system is designed with the speed loop as the outer loop and the acceleration loop as the inner loop.In addition,the cascade double closed-loop PID control method is employed to design the anti-rolling control system.Finally,in order to verify the feasibility and anti rolling effect of the control method and mechanism in practical engineering application,a pool test is carried out with a six meters ship model which equips four lifting units to verify the control method and the anti-rolling effect of the mechanism.Wave generator offers wave external excitation rolling at zero speed.The gravity slider provides the external excitation rolling at forward speed.A series of working conditions are designed for the model at zero speed and forward speed.The performances of anti rolling with different parameters such as swing speed,swing speed ratio and swing angle are obtained.The speed test finds out the swing critical speed of Magnus effect anti rolling device.During the test,the anti rolling performance increases sharply in the range of below critical speed and remains unchanged after reaching or exceeding the critical speed.According to the experiment,the results concludes a maximum of 89.8%anti-rolling efficiency at zero speed and a maximum of 96.9%anti-rolling efficiency at forward speed.An additional zero speed test is carried out to determine the redundancy degree of the anti roll system when several lifting units lose efficacy,which provides guidance for the anti roll scheme under the special operation conditions of the ship.The effective anti roll of three-bar is 86.18%,and the minimum effective anti roll of two-bar is 73.59%.