细长体水下运动空化流场及弹道特性实验

Experiment of cavitation and ballistic characteristics of slender body underwater movement

为了研究细长体水下高速运动时空泡的产生、闭合及脱落特性,及影响细长体空泡形态及弹道特性的复杂因素等,初步开展了细长体模型水下高速运动的实验研究,分析了不同初始空化数下细长体模型在水中高速运动的一系列流动现象,重点研究了空泡的发展、闭合、尾部回射流和尾部脱落特性,以及轴对称细长体模型弹道特性与空泡形态变化之间的关系和转动特性随时间的变化历程等。结果表明:细长体水下高速运动时形成超空泡,空泡头部光滑透明,尾部凝结有汽水混合物且有交替脱落的含气漩涡;初始空化数对细长体的速度衰减有所影响;受初始扰动影响,细长体水下运动伴随有绕头部的转动且初始扰动影响细长体俯仰角随时间的变化历程。

Experimental studies of the slender body＇s underwater movement were conducted using high-speed camera. Based on the results from the experiment, we examined the characteristics of the cavitation and ballistic of the slender body moving underwater. The experimental results show that the slender body＇s underwater movement is accompanied with a supercavity, and the slender body＇s movement and rotation occur in the supereavity except for the contact between the slender body＇s head and the supereavity wall and the supereavity wall is transparent and smooth except for its tail. The impact between the tail of the slender body and the supercavity wall results from the slender body＇s rotation in the supercavity, called the tail slap, which serves to stabilize the slender body＇s movement in the supercavity as a result form the initial perturbation of the flow field. The cavity evo- lution, closure and shedding were discussed in detail. Series of different flow mechanisms and the re- lationship between ballistic characteristics and cavity morphology were also analyzed with different ini- tial velocities. The slender body has different accelerations with different initial velocities and the effect of the drag reduction using super cavitation is influenced by factors such as cavity length, diam- eter and aspect ratio, etc. The initial perturbation angle affects the variation of the angle between the slender body and the cavity axis.