Research On Water Entry Hydrodynamic And Trajectory Characteristics Of High-speed Projectiles

The water entry process of high-speed projectiles involves many complicated physical phenomena, such as cavitation, turbulence and passing through the free surface, it is characterized by high-load, unsteady situation and nonlinear behavior, it also need to go through different motion stages, e.g. water impact and tail slapping. The trajectory and hydrodynamic characteristics during the process of water entry are affected by many factors. This thesis discusses the trajectory and hydrodynamic characteristics during the water entry process of high-speed projectiles by using self-programming trajectory simulation and numerical methods systematically. The main topics of this thesis are as follows:The stress state before and after water entry of high-speed projectiles has been analyzed based on water entry ballistics and hydrodynamics. The secondary causes which influence little on overall trajectory have been ignored, then we got the simplified force model. The dynamics model of projectile longitudinal motion has been built using the modeling method of torpedo navigation mechanics and combining the projectile tail force formula during tail slapping derived by conservation of momentum theorem.The hydrodynamic characteristics during water entry of high-speed projectiles have been discussed using numerical simulation method based on RANS(Reynolds-averaged Navier-Stokes equations) and moving computational domain technology, meanwhile introducing VOF multiphase flow model, k - e turbulence model and Schnerr cavitation model, then we got the change rules of angular, cavitation, cavitation wall surface velocity, bullet pressure, and so on.Combining numerical simulation results the dynamics model has been used to compile trajectory simulation program by MATLAB, the trajectory simulation during water entry process of high-speed projectile has been estimated then. We investigated the change rules of pitch angle, pitch angle velocity, trajectory and velocity of focus, analyzed the characteristics of tail slapping and got the trajectory characteristic influence regulation of initial angle velocity, projectile density and water entry angle.