Research On The Cavitation Evolution And Load Characteristics During The Fluid-structure Interaction Of A High-speed Vehicle Crossing The Water Surface

With the development of military research,the launching mode of underwater vehicles which can be launched by submarines,ships,helicopters,fighter jets,and road missile systems,tends to be flexible.The change of launching form inevitably brings new challenges to the research and development of vehicle.Transmedia problems will be encountered in the water entry process.The vehicle enters the water in a very short time when hitting the surface of the water and rapidly displacing the surrounding fluid.The fluid exerts a strong reaction force on the structure.The extreme impact load at the initial stage of water entry is a physical process that cannot be ignored.At the same time,the energy conversion of entering water and hitting water surface promotes the formation of cavitation.The interaction between cavitation and projectile body forms the slamming load when the trajectory of the projectile will change significantly at the late stage of water entry.Therefore,the cavitation evolution and the shock load formation of water entry of the vehicle has become an important topic in combat research and development.Based on the theory of fluid mechanics,structural mechanics and fluid-structure interaction,this paper studies the fluid-structure interaction of a vehicle entering water by using an arbitrary Lagrange euler method(ALE)and Ansys softwar.The cavitation evolution law,the impact load law,and load reduction law in the process of vehicle crossing medium are investigated and analyzed.The motion coupling characteristics and the mechanism of many parameters in the process of high-speed vehicle crossing the water surface are revealed,which provides reference for the design and manufacture of a vehicle crossing the water surface.Firstly,the ALE numerical method theory,fluid-structure interaction interface processing method and feasibility of numerical method are described.Then,combined with the basic theory of high-speed water entry cavitation,the established numerical model of navigation body was used to simulate the evolution process of cavitation and the evolution law of high speed water entry cavitation are studied.The influences of initial entry conditions on the cavitation evolution characteristics of projectile body were summarized.Finally,based on the original projectile type,the slenderness ratio and the head shape of the projectile body configuration are improved to achieve the goal of dropping the load of projectile body crossing the water surface.Combined with the characteristics of impact load and cavitation evolution,the formation process of impact load of the projectile with the improved configuration in the process of high-speed water entry was comparatively studied,and the mechanism of trans-medium load reduction of the improved configuration projectile was proved,which provided basic technical support for the research and development of the highspeed transmedium vehicle for realizing the load reduction of the projectile crossing the water surface.