The Study On Influence Of Hover System On Hydrodynamic Performance Of Partial Air Cushion Supported Catamaran

With the development of the world's ship industry and the technological innovation of military ship design,new high-performance ships have appeared contuinously.Among them,the PACSCAT(Partial Air Cushion Supported Catamaran)has performed remarkablely with the characteristics of new type and excellent performance.It provides an effective solution for navigation and fight in high velocity,high-efficiency load and shallow water.As an important component of the PACSCAT,the hover system includes a series of devices that form cushion of the PACSCAT.The cushion pressure and air flow are the key factors to affect the hydrodynamic performance of the hovercraft.Therefore,in this paper,the methods of model test and numerical simulation are combined to study the method of forecasting the resistance of the ship,and the resistance characteristics are explored to provide a reference for the research and optimization of ship types.In this paper,the classifications of the hover system in a broad sense were described.The domestic and international progress in the design and research of the PACSCAT,its similar type of ship resistance forecasting method and hover system were reviewed.Based on the research objects and research methods of this paper,the theories and methods of the research on the PACSCAT were comprehensively expounded.The resistance characteristics of PACSCAT were studied according to the model test.The variation rules of resistance,pitch,heave and velocity were summarized.From the perspective of total resistance,the influences of cushion pressure and the air flow on the resistance performance of PACSCAT were analyzed.Through the analysis of the navigation state and resistance of PACSCAT and wave characteristics,the optimal air flow and fan regulation program were chosen.With the theory of planning plate,the influence of the immersion length,velocity and attack angle of simplified bow seal on the wave-making of free surface of PACSCAT was studied,and the pressure distribution of the bow seal under hydrodynamic pressure and air cushion pressure was studied.The variation of resistance coefficient and the lift coefficient with the change of air cushion pressure were given.The simulation of the bow seal with the rubber material was carried out based on the bidirectional fluid structure interaction method.The seal pressure,seal deformation,the variation of resistance and the influence of seal on the waveforms of free surface after the deformation were analyzed.Based on the theory of mechanics of viscous fluids,a numerical simulation method for predicting the motion of PACSCAT with high precision was established.By means of numerical simulation,the three dimensional flow characteristics of the PACSCAT(the plenum chamber,the hover air chamber and the airbag flow duct)were simulated.The numerical simulation results and the experimental data were compared.Based on the established numerical simulation results,the contrast analysis of the cushion wave making inside and outside the hover system was analyzed.With the influence of cushion only,the influence law of the resistance and navigation state of PACSCAT was analyzed.The improvement method of the spilt-cushion technology and the splitter plate in the plenum chamber for gas flow was analyzed in detail to improve the performance of resistance.The results show that the improvement of the air cushion partition technology and the air chamber stabilization had played an important role in the regulation of cushion pressure distribution,with the average high-speed resistance reduction rate of 22%.