Study On Trajectory Characteristics And Motion Stability Of The Vehicle During High-Speed Water Entry

The high-speed water entry of the vehicle involves the cross-medium process from air to water.The sudden change of the medium makes the trajectory of the vehicle change greatly after water entry,and the motion instability increases,which makes the trajectory instability of the vehicle occur during the water entry,and greatly affects the motion attitude of the vehicle.In order to disclose the trajectory characteristics of the vehicle at high speed and ensure its motion stability,the numerical method is used to systematically study the trajectory characteristics and motion stability of the large-scale vehicle at high speed.Firstly,the coordinate system describing the motion of the vehicle is selected based on trajectory theory of water entry,the motion parameters and attitude parameters of the vehicle are given,and the force analysis is carried out for the process of the vehicle during water entry.At the same time,a numerical simulation method for trajectory of water entry is established based on FLUENT platform.The moving domain method and self-compiling program are used to realize the motion of the vehicle during water entry,and the grid convergence is verified,the validity of the numerical simulation method is verified by the relevant experiment results of water entry.Secondly,based on the established numerical simulation method,the influence of water entry parameters on the water entry trajectory of the vehicle is carried out,and the characteristics and motion law of the vehicle’s trajectory under high-speed vertical water entry,different water entry angle and different water entry velocity are analyzed.The results show that the vehicle is easy to occur the side surface motion with sticking water under small angle of water entry,the trajectory towards the water surface is easy to appear at high speed.Thirdly,the influence of the structural shape of the vehicle on the water entry trajectory of the vehicle is studied.The influence of the head shape,aspect ratio and tail rudder structure of the vehicle on trajectory characteristics and motion law during high-speed water entry are analyzed.The results show that the flat-ogive head type has good water entry trajectory characteristics,the large aspect ratio is easy to appear the arc trajectory with large curvature,and the tail rudder structure cannot completely improve and enhance the motion stability of the vehicle during water entry.Finally,according to the research conclusion of water entry trajectory under different conditions,the control measure of the vehicle’s motion stability during water entry is studied,and the influence of tail stabilizer on the motion stability of water entry is studied.Based on the assumption of the tail stabilizer proposed by the researcher,the improved design is carried out and the tail expansion type of the wrapped tail stabilizer is obtained.The effect of the wrapped tail stabilizer on the stability of the large-scale vehicle at high-speed water entry is studied.The results show that the wrapped tail stabilizer improves the motion stability of the vehicle during water entry,and the wrapped tail stabilizer makes the motion of the vehicle more stable after water entry,which is better than the assumption proposed by the researcher.The research conclusions obtained have important guiding significance for improving the motion performance of torpedo and other weapons during water entry,and can provide certain technical support for the development of cross-medium aircraft and control of water entry trajectory.