Numerical Study On Characteristics Of Oblique Water Penetration Of Slant-headed Projectile Across Medium

In recent years,the international situation facing our country has become increasingly complex,and maritime frictions such as the Diaoyu Islands issue and South China Sea disputes have increased.Therefore,the development of weapons and equipment technologies such as naval ships and helicopters is still an indispensable part of the national defense and military system.Among them,the small-caliber supercavitating projectile is a new type of weapon.Since the projectile enters the water across the medium,it needs to cross the interface between the gas phase and the liquid phase,which will produce complex hydrodynamic phenomena and will also be affected by the nearby free liquid surface.This makes the hydrodynamic characteristics of the projectile moving across the medium very complicated and difficult to study.At present,there are relatively few studies on the entry process of oblique frustum projectiles with chamfered angles in our country.Therefore,the numerical simulation of the water penetration characteristics of the slant-nosed projectile can provide an important reference for the development of related weapons and equipment in my country.In this paper,by coupling 6-degree-of-freedom ballistic equations and computational fluid dynamics equations,using density box for mesh refinement,combined with dynamic mesh technology,numerical research is carried out using VOF multiphase flow model,RANS turbulence model and cavitation model.The feasibility of the calculation method in this paper is verified by comparing the experimental and numerical results with related literature.Numerical simulation studies on the entry process of different head-shaped projectiles at different water entry speeds and water entry angles were carried out.The effects of different conditions on the cavitation shape,ballistic characteristics and fluid dynamics of the projectiles were analyzed,and the head-shaped,The mechanism of velocity and water entry angle on the underwater trajectory deflection of the frustum-nosed projectile is as follows:(1)The projectile has a tendency to raise its head under different speed conditions.The projectile gradually turns flat.The faster the projectile is subjected to more pressure and the generated torque is also greater.The greater the change in the pitch angle of the projectile,the flattening the projectile.The faster,the faster the tail motion frequency and the shorter the period.(2)Flat-headed bullets generate cavitation earlier,but the rate of cavitation formation is relatively slow,and the closing time is longer;the 15° cut-angle projectile is wetted first when the head is not completely wetted,and the cone of the projectile is wetted first.The cavitating bubble does not gradually develop from the head to the tail,but the head and the cone begin to generate at the same time.Therefore,the front-end cavitation is generated slowly;the pitch angle of the 30°-cut projectile has the largest change,followed by the 15°-cut projectile.The flat head has the smallest change.(3)The smaller the water entry angle,the faster the cone and the tail end of the projectile are wetted,but the deflection amplitude is smaller,that is,the 15°water entry projectile has the earliest tail shot phenomenon,and the 45°water entry projectile occurs the latest.