Research On Motion Characteristics Of Air Cushion Vehicle

Air cushion vehicle is a high-performance ship which relies on air cushion to hold up the whole hull and can sail above the water surface at high-speed.Due to its special working principle,air cushion vehicle has prominent high-speed and amphibious capability.Meanwhile this particular working principle in turn leads to the result that the air cushion vehicle movement is a complex nonlinear and multiple degrees of freedom dynamical system which involves the coupling interactions of hull,skirt,air cushion and water.Therefore,to conduct the thorough research on the movement characteristics of air cushion vehicle is a common requirement for technology development and national needs,which has the quite high academic value and strategic significance.First of all,three key technologies that impact movement characteristics.of air cushion vehicle have been discussed and studied in this paper which involve wave-making waveform,air cushion system and skirt system.And then,the six degrees of freedom nonlinear maneuvering motion model of air cushion vehicle has been established.Finally,the evaluation index of beach-landing motion has been put forward,and the beach-landing motion of a certain type vehicle has been calculated and evaluated by using the established simulation model.Based on the linear wave theory and the wave-making calculation method of rectangular uniform pressure distribution,the wave-superposition method to study the wave-making calculation model of multi-chamber air cushion is adopted.On the basis of multi-chamber calculation method,the air cushion is divided into a number of discrete air chambers along the length and width,assuming that the pressure within each chamber unit is uniformly distributed.Then the wave-superposition processing method of multiple air chambers is used to obtain the wave-making wave form calculation method of non-uniform pressure distribution.Finally,the air cushion wave-making waveforms of multi-chamber and non-uniform pressure distribution are calculated with the above calculation method,and the rationality of the calculation method is verified.Aiming at the deficiencies of the existing theories,this paper analyzes the mechanics mechanism of air flow within the air cushion,and the air cushion system dynamics model which can reflect two-dimensional pressure distribution condition inside the air cushion has been established according to the idea of average vertical pressure distribution.On this basis,the air pressure distribution calculation model is established by using the discrete calculation method.Aiming at the deficiencies that the skirt dynamics calculation model does not consider the situation of skirt bag contacting water,based on non-momental theory of flexible thin shell,the theory that regards the external force imposed on the skirt as the superposition pressure distribution with a certain regularity which combines the air pressure with water buoyancy force is proposed.The dynamic model of binary single bag skirt which covers the situation of skirt bag contacting water as well as skirt finger contacting water is established,and the formation and deformation mechanism of binary single bag-finger skirt is studied by using the discrete calculation method.In addition,the variable pressure distribution area which appears below the double bag closure finger skirt on the skirt movements has been analyzed,and the responding formation and deformation of binary skirt have been done the simulation calculation.Finally,according to those binary skirt researching results,a three-dimensional dynamic model of the skirt system is established.After a detailed analysis of forces in the movement of air cushion vehicle,based on the MMG model theory of vehicle manipulation,the maneuvering movement mathematic model of nonlinear six degrees freedom is established which involves the movements of hull,skirt,air cushion and water.The simulation program is compiled,and the motion characteristics are also calculated.By comparing with the full scale test data,we firmly verify the rationality of the maneuvering motion mathematic model,and the simulation accuracy standard meets the requirement of both engineering design and actual use.Based on the detailed study related to the beach-landing motion characteristics of the air cushion vehicle,the factors which affect the beach-landing motion properties are summarized,and the evaluation index of beach-landing motion is proposed.By using the established maneuvering movement mathematical model of nonlinear six degrees freedom,the beach-landing motion characteristics of a certain air cushion vehicle with specific weight has been conducted simulation calculation and analysis,and the beach-landing motion has also been evaluated in detail.