A Study of Ultra-High Speed Liquid Flow Phenomena Using a Light Gas Gun

利用轻气炮立式成型装置对超高速液体流动现象进行了实验研究。首先，我们进行了初步实验，得到了火药质量与弹托飞行速度之间的关系。利用2G塑料弹托飞片，获得了从几百米每秒到2公里/S的飞片速度，在此基础上，我们将上面的一片飞片送入水中，观察到了自由面变形、表面闭合和飞溅等一系列表面现象。我们还观察了物质进入水中后形成的空穴的行为。在物质运动的后期，一个空穴充分发育，最终从表面分离出来。分离后，在闭合空腔的后侧出现了一个有趣的现象--可再入射流。它正朝着物质流动。这种实验是针对两个测试液…进行的更多的ID，水和甘油，以评估液体的粘度。此外，我们还发现，在此过程中产生的空化气泡受到相邻空泡表面的强烈影响。针对这一问题，对自由表面附近激光产生的气泡进行了实验研究。因此，我们得到了一些关于气泡迁移的信息，即自由表面排斥从边界坍塌的气泡。另一方面，我们还研究了超高速液体流动现象的典型例子--脉冲水射流问题。一只1.15g的塑料弹托正面有一条携带少量水的沟渠，撞击到弹托上，分离出的水由于惯性作用，穿过弹托内的一个小孔，如喷嘴，最终以1.5公里/S的最大速度撞击设定在真空状态下的靶标。从喷嘴出口出来的脉冲射流在混合层变得不稳定，产生大量微小的液滴。我们在靶材表面观察到了大量的微观侵蚀，即所谓的损伤坑。它们必须是由于单个液滴的高速撞击而形成的。较少

An experimental study was made of the problem concerned with the ultra-high speed liquid flow phenomena by means of a vertical from of light gas gun. First we conducted a preliminary experiment to obtain the relationship between powder mass and sabot flyer velocity. Using a 2g plastic sabot flyer, we obtained the flyer velocity ranging from several hundreds meters per second up to 2km/s. Based on the data obtained, we rushed a flyer from the above into water and observed the sequential surface phenomena such as the deformation of a free surface, the surface closure and the splash. We also observed the behavior of a cavity formed behind the substance moving into water. In the later stage of the substance movement, a cavity was fully developed and finally separated from the surface. Aftre the separation, an interesting phenomenon, a reentrant jet, occurred at the rear side of the closed cavity. It was flowing toward the substance. This kind of experiment was carried out for two test liqu … More ids, water and glycerin, in order to evaluate the liquid viscosity. Furthermore we found that cavitation bubbles generated during this process were strongly influenced by the adjacent cavity surface. In relation to this problem, an experimental study was made of a laser-produced bubble near a free surface. Consequently, we had some information about the bubble migration such that a free surface repels a bubble collapsing from the boundary. The behavior of two bubbles not only in phase but ou t of phase was also experimentally examined in detail.On the other hand, we investigated the problem of a pulsed water jet which belongs to be one of the typical examples of ultra-high speed liquid flow phenomena. A 1.15g plastic sabot, which has a ditch at its front side for carrying a little amount of water, impacts on a sabot stopper, thereafter theparated water goes ahead through a small hole inside the sabot stopper, like a nozzle, due to the inertia and finally impacts with the maximum velocity of 1.5km/s against a target which was set in the vacuum state. A pulsed jet emerging from the nozzle exit becomes unstable at the mixing layer, producing a large number of minute droplets. We observed a lot of microscpic erosion, so-called damage pit, on the surface of the target. They must be formed due to the high speed impacts of individual droplets. Less