Research On Hydraulic Water Hammer Caused By High-speed Fragments Hitting A Liquid-filled Container And Its Damage Mechanism

In this dissertation,the formation process of hydrodynamic ram,the characteristics of the air cavity in the liquid,the pressure distribution,the decay law of the fragment velocity,the deformation of the container walls and the effect of the liquid filling ratio,the kinetic energy of the fragment and the liquid type on hydrodynamic ram were studied by numerical simulation and experiment.The fragment penetrates the front wall of the liquid-filled container,impacts the water surface and forms a hemispherical wave which propagates forward along the direction of the fragment motion.The pressure at different azimuths of the initial shock wave front varies.The velocity of fragment in water can be expressed as an exponential decay;the conical air cavity forms behind the fragment,its diameter and length increase with fragment motion.The results show that the cavity length-diameter ratio increases with fragment motion first and approaches 4.77?4.84 finally.The pressure on the head of the fragment is the largest,and the pressure on both sides is symmetrically distributed along the direction of movement of the fragment.As the fragment moving,the pressure increases in the liquid.The damage degree of the container walls is different as the impact kinetic energy of the fragment varies.With the increase of the kinetic energy of the fragment,the damage degree of the front and rear walls can be divided into three grades,that is,no crack occurs on the front and rear walls when the kinetic energy is less than 1191J;cracks only appeared on the back wall when the kinetic energy is between 1191J and 8152 J,cracks appeared on the front and rear walls,and the rear wall was petal-shaped when the kinetic energy is larger than 8152J.The higher the kinetic energy of the fragment impacts,the more the total number of cracks in the walls.In the process of fragment impacting the water-filled vessel,diesel oil and aviation kerosene respectively,the hydrodynamic ram in water has the most serious damage to the container,followed by diesel,and the container walls with kerosene is the smallest.With the filling ratio of the container increasing,hydrodynamic ram damage to the walls gradually increased.