Numerical Study On The Impact Characteristics Of Anti-submarine Missile’s Cushion Nose Cap Into Water

The water entry process of anti-submarine missile involves the multiphase flow of gas,liquid and solid.The missile body experiences medium mutation at the moment of water entry,which will produce a great impact load,which will cause the destruction of the missile body structure and the failure of internal instruments.Therefore,it is necessary to study the water entry process of the missile body.In this paper,the fluid-structure interaction analysis is carried out for the water entry of anti-submarine missile and its Cushion nose cap.The impact load characteristics of the missile body and the cushioning performance of the Cushion nose cap are studied,which provides some guidance and reference for the protection of the anti-submarine missile and the design of the Cushion nose cap.In this paper,LS-DYNA software is used to numerically simulate the missile body into water based on ALE(Arbitrary Lagrange-Euler)method.At first,the numerical calculation method is verified to ensure the rationality of the calculation method.On this basis,threedimensional numerical simulation was carried out for the missile body entering water at different speeds and angles,and the pressure distribution and impact load variation law of the missile body in the process of entering water were obtained.The results show that the maximum overload,peak pressure,peak stress and head deformation of the missile body increase with the increase of water entry velocity,and at different velocities,the maximum stress of the projectile exceeds the yield strength of the missile body material,and irreversible damage occurs to the missile body.As the inlet angle decreases,the maximum overload,peak pressure,peak stress and head deformation of the missile body all decrease.When the inlet angle exceeds 60°,the missile body cannot safely enter the water.It is a fast and effective method to add a Cushion nose cap to the missile body to ensure its safe entry into water.Based on the previous results,this paper established the finite element model of anti-submarine missile carrying cushion nose cap into the water.On this basis,the crushing process and buffering principle of the cushion nose cap are analyzed,and the influencing laws of buffering performance of the Cushion nose cap are studied,including water inlet velocity,water inlet Angle,length of the cushion,elastic modulus of the cushion and number of pre-formed grooves for nose cap.The results show that the cushion nose cap can effectively reduce the impact load and improve the reliability of the missile body when it enters the water.The larger the inlet velocity is,the smaller the inlet angle is,and the worse buffering performance of the cushion nose cap is.Increasing the cushion length can obviously improve the buffering performance of the cushion nose cap.The smaller the elastic modulus of the cushion,the softer the cushion,the better the cushioning performance of the cushion nose cap.Pre-formed groove structure can improve the crushing capacity of the nose and make the cushion nose cap more easily broken.