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

用轻气枪垂直射出的方法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，得到了火药质量与射弹飞行速度的关系。使用2g的塑料弹片，我们获得了从几百米每秒到2公里/秒的飞行速度。根据获得的数据，我们将上面的飞片放入水中，观察了自由表面变形、表面闭合和飞溅等顺序表面现象。我们还观察到物质进入水中后形成的空腔的行为。在物质运动的后期，一个空腔充分发育，最终从表面分离出来。在分离之后，一个有趣的现象，即在封闭腔的后侧出现了一个可重入射流。它正流向物质。以水和甘油两种测试液体为实验对象，对液体粘度进行了评价。在此过程中产生的空化气泡受到邻近空腔表面的强烈影响。针对这一问题，对靠近自由表面的激光产生的气泡进行了实验研究。因此，我们有一些关于气泡迁移的信息，这样一个自由的表面排斥气泡从边界崩溃。对两个气泡在相内和相外的行为进行了详细的实验研究。另一方面，我们研究了脉冲水射流的问题，它属于超高速液体流动现象的典型例子之一。一个1.15克的塑料弹壳，在它的前面有一个沟渠，用于携带少量的水，撞击在一个弹壳塞上，此后分离的水通过一个小洞在弹壳塞里，像一个喷嘴，由于惯性，最终以1.5公里/秒的最大速度撞击在真空状态下设定的目标。从喷嘴出口出来的脉冲射流在混合层变得不稳定，产生大量的微小液滴。我们在目标表面观察到很多微小的侵蚀，也就是所谓的损伤坑。它们一定是由于单个液滴的高速撞击而形成的。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