Numerical Simulation For The Hydrodynamic Characteristics Of Water Entry Process And The Effect Of Elasticity

Maritime military forces are of paramount importance in safeguarding state sovereignty and protecting the integrity of our territorial waters.In order to solve the problem of underwater defense difficulties,high-speed water entry weapons have been invented one after another recently with the developing and application of the supercavitation.The projectile is launched in the air and travels across the interface into the water.This is a very complicated physical phenomenon which must meet or be compatible with airborne,cross-medium and underwater flight stability conditions at the same time.Moreover,the experiment is very difficult and requires a lot of manpower and resources.With the development of computer technology and visualization technology,numerical simulation has gradually been applied to supercavitation research which has the characteristics of high efficiency,high precision and low cost.Great progress have been made for supercavitation technology,but there are still many problems left for us to solve up to now.Above all,the numerical simulation in this paper mainly focuses on the following aspects: The effect for head shape of rigid cylinders on the size and flow field of water entry supercavity.The effect for length-to-diameter ratio and Young's modulus of flexible cylinders on supercavity flow field and the water entry movement law.The effect for head shape of flexible cylindrical shells on supercavity flow field,shell deformation and shell pressure distribution.The specific content is as follows:(1)In order to obtain the surface closure time and the formation and development of the projectile model water entry supercavity,a 2D numerical simulation for modeling the supercavity induced by the rigid cylinders with different heads and a practical projectile model is performed based on Fluent 15.0.The effect of the head shape on several respects such as the closure time,the velocity flow field around the cylinders and the supercavity size is analyzed.The supercavity profile result of the practical projectile model have a good agreement with the Logvinovich semi-empirical formula.(2)In order to study the interaction between the supercavity flow field and elasticity cylinders,a Fluid-structure interaction simulation is carried out for modeling the water entry process of elasticity cylinders with different length-to-diameter ratios and Young's modulus based on the finite element software ANSYS/LS-DYNA and ALE(Arbitrary Lagrange Euler)method.There are some results are obtained such as the development of the supercavity shape and the velocity and acceleration change of the elasticity cylinders.(3)In order to study the interaction between the supercavity flow field and elasticity clindrical shells,a Fluid-structure interaction simulation is carried out for modeling the water entry process of elasticity cylindrical shells with different cone angles based on the finite element software ANSYS/LS-DYNA and the ALE method.There are some results are obtained such as the influence of the heads on the supercavity shape,the change of velocity and acceleration for the elasticity clindrical shells,the deformation of the upper and lower surfaces of the elasticity clindrical shells and the pressure distribution on the lower surface.The numerical simulation is carried out for modeling the water entry process of rigid&elasticity cylindrical shells and cylinders and the results are analyzed.The results of this article can be referenced for the water entry supercavity of high-speed projectiles in experimental study and numerical simulation by summarized the conclusions of this paper.