Influence Of Interceptor On Ship Hydrodynamic Performance And Simulation Of Active Control Pitch Stabilization

The 21 st century is the century of ocean,and the new era puts forward higher requirements for the design and construction of modern ships.Nowadays,people not only attach importance to the speed,seakeeping and maneuverability of ships,but also pay more attention to the economy and environmental protection.Installing proper appendages for ships can improve hydrodynamic performance at a lower cost,and the interceptor is exactly a good choice.The interceptor is a kind of ship appendage installed on the stern of the ship,which common shape is a straight plate perpendicular to the waterline,and it is also called as spoiler,stern plate,etc.At present,interceptors are mostly used on the medium and high-speed ships.At high speed,interceptor will disturb the water flow to generate lift in the stern part of the ship,regulate the trim,and effectively reduce ship resistance.The use of active control interceptor can provide real-time changeing lift,restrain the ship pitch and roll,and it can also improve the maneuverability.Until now,the research about interceptor mainly focused on the trimming and drag reduction effects of interceptor with different parameters in still water but not on the anti-pitching effects,by the method of numerical simulation and model test methods.While for active control of anti-pitching,researchers mostly used model test methods to explore the anti-pitching effect of interceptors on specific ships,which is susceptible to the influence of equipment and it is difficult to reflect the real anti-rolling effect.And now there is still no research using CFD method to simulate active control anti-pitching with appendages.In this dissertation,a landing craft model which design speed is in the transitional stage was taken as the research object,then a series of numerical simulations about the influence of interceptor on resistance,pitch and heave motion in still water and waves were made.On this basis,the method of how to achive the numerical simulations on the active control of interceptor anti-pitching were probed.The main research contents and conclusions of the article include:(1)The CFD numerical simulation on the ship model with interceptor were performed,and it was compared with the test results to comprehensively consider the best grid plan,then the speed,depth and shape of interceptor were changed to discuss the influence of interceptor on hydrostatic resistance,trim and heave motion under different working conditions.The good drag reduction and trim adjustment effect of interceptor with suitable depth on the ship model at higher speeds was verified,and found there is a best depth of interceptor that can minimize the resistance of ship model at a certain speed;(2)Based on the CFD method,a numerical wave pool was constructed to analysis the influence of interceptor about the resistance,trim and pitch motion when the ship model were sailing in regular head waves,in terms of resistance component,wave steepness and speed.It was found that interceptor still had the effect of reducing drag and adjusting the trim in those waves.The total resistance in those waves were still reduced,although the coefficients of added resistance were promoted,and the increase of resistance in wave is mainly due to the increase of the pressure resistance;(3)In order to choose a better calculation scheme,several grids were designed and compared,then the numerical simulation of active control anti-pitching with interceptor was realized in this scheme.Compared the anti-pitching effects of actively controlled interceptor with different active control laws and motion ranges,when the ship model were sailing at different speeds in regular waves of different wavelengths.Through analyzing the details of the flow field,the hydrodynamic mechanism of active control anti-pitching with interceptor,then it was found that the interceptor with active control has a better anti-pitching effect than the fixed interceptor,at the same time it can reduce resistance.The research in this dissertation can provide analysis about the influence of interceptor on hydrodynamic performance of the ship in still water and waves,and the control strategy of interceptor during actual navigation.It can also provide feasible ideas for the exploration about CFD numerical simulation of active control with the interceptor or other anti-pitching appendages.