Study On The Cavitation Fluid Properties Of High-speed Projectiles Across Media Into Water

When a projectile enters the water at high speed,the water flow in the low pressure region on its surface will vaporize,and then form a cavity with other gases such as air,it is called cavitation phenomenon.Cavitation is a unique fluid-solid coupling phenomenon,which is widely used in underwater weapons drag reduction research and other fields.The cavitation of the projectile occurs immediately after entering the water at high speed,and the attached cavity of the projectile under the condition of multi-phase flow coupling shows a strong nonlinear change and non-constant development,while the fluid distribution inside the cavity changes with the continuous evolution of the projectile cavity.The study of the water entry of high-speed projectiles under different motion parameters can effectively provide reference for the design of super-cavitation underwater weapons.In this paper,a combination of numerical simulations and experiments is used to calculate the water entry of high-speed projectiles across media,and the main research contents are as follows:A high-speed projectile water entry experiment was conducted with the projectile water entry velocity as a variable.The experimental platform of high-speed projectile entry was built.Captured the complete process of projectile navigation in water at different velocities and the evolution of the cavity.Analyzed the scientific principles behind the different cavitation phenomena under the influence of velocity.And gave and analyzed the change curves of relevant parameters such as vacuole diameter,drag coefficient and velocity decay coefficient with time.Numerical computational models were established,and computational method validation and irrelevance validation were carried out.Based on the Realizable k-εturbulence model and the VOF multi-phase flow model,a numerical computational model for the process of high-speed projectile cross-media water entry is established.The calculation results were compared with the results of the subsequent experiments on the entry of the projectile into the water,and the verification of the numerical method was carried out,and the numerical simulation results matched with the experimental test results,which verified the accuracy of the calculation model.Further verification of the irrelevance of parameters such as the number of meshes,time steps,and turbulence models was carried out to finally determine the appropriate parameters and carry out the computational analysis of the high-speed projectile into the water under different motion parameters.A new method for defining the cavitation stage is proposed,and the influence law of different parameters on the cavitation stage is summarized.A new method for defining the cavitation stage is proposed based on the distribution law of the fluid in the projectile with time after the projectile enters the water under the initial conditions,and this method is used as a benchmark to carry out subsequent studies on the effects of different parameters on the cavitation process of the projectile entering the water.The projectile entry pitch angle,entry velocity and entry spin velocity were analyzed from the three factors of projectile entry.The hydrodynamic and fluid cavitation characteristics of the projectile after entering the water are mainly discussed,and the trends of the relevant parameters such as the diameter of the projectile vacuole,the length of the vacuole,the volume of the fluid inside the vacuole and the drag coefficient with time are given,and the natural laws behind them are discussed and summarized.