Experimental investigation into low-velocity water entry of cylinder structure

The process of low-velocity water entry is utilized on a large scale for the military and engineering purposes. However, there are rarely systematic experimental investigations into the low-velocity water entry of cylinder structure for reference. In order to obtain typical phenomena and relevant laws, we design a set of experimental facilities with adjustable parameters and better repeatability to study this process with a high-speed photography system. The influences of cylinder radius, initial velocity and entry angle on the process of lowvelocity water entry are tested. Results show that six typical phases exist in this process: structure submersion,necking, cavity formation, cavity abscission, spray at the free surface and jet formation. Three factors mentioned above are key parameters and influence the process in different degrees, and some laws obtained in this paper have a reasonable agreement with the theoretical results. Our results provide references for the relevant numerical researches and engineering applications.     

激波作用下R22气泡射流现象研究

  目的  为了研究自由液面、气泡与冲击波三者之间的相互作用,  方法  基于间断迦辽金法,结合Level Set与Real Ghost Fluid方法,分析复杂流场中冲击波传播特性及气泡运动特性,描述流场内各种波系的生成与发展过程。  结果  结果表明：在相互作用过程中,流场生成的复杂波系中包含多个稀疏波和冲击波。自由液面减缓了气泡的溃灭速度,而入射冲击波则加快了气泡的溃灭速度,并使自由液面的上拱运动增大。  结论  所得结果可为水下爆炸对舰船结构的毁伤机理提供参考。