The Research On The Forming Mechanism Of Liquid Jet In Shallow Water Explosions

With the attention to the coastal operations,the interface effect caused by shallow water explosion has aroused the interest in the field of military.Due to the effect of water-air interface and water-bottom interface on the shock waves and bubble,the shallow water explosion has a lot of complex phenomena,and the liquid jet phenomenon is the most important one,of which the essence is still undiscovered.To explore the forming mechanism of liquid jet in shallow water explosions,this paper sets up a small TNT equivalent underwater explosion system and a spark bubble experiment platform under laboratory conditions,referencing the previous techniques.Experimental researches on small TNT equivalent underwater explosion in water tank and spark bubble-free surface interaction on different depth are done and the dynamic images for the bubble oscillation and the liquid jet forming process are obtained using high-speed camera.And then the shallow water explosion processes are studied numerically using simulation software.Based on the experimental data,the interactions process and the evolution law of bubble and free surface are summarized,and the key factors affecting the formation of liquid jet are obtained.By comparing the bubble migration and surface uplift under different scaled distances,the decisive factors influencing the shape and velocity of liquid jet are obtained,as well as the liquid jet speed variation law versus scaled distance.By arranging the formation process of water jet,seven typical stages of the bubble and free surface interaction process and three types of superposition of the water surface plume disturbed by the first and second bubble pulse are summarized.These conclusions can well explain the phenomena observed in experiments,and can provide a new vision and reference to the research of liquid jet formation mechanism.