Experimental Investigation of Shock-Bubble Properties at the Liquid–Air Phase Boundary
Experimental Investigation of Shock-Bubble Properties at the Liquid–Air Phase Boundary
复制标题
液-气相界冲击气泡特性的实验研究
DOI：
10.1007/978-3-319-44866-4_63
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
U. Teubner
中科院分区：
文献类型：
--
作者：
W. Garen;B. Meyerer;Y. Kai;W. Neu;S .Koch;U. Teubner
在靠近液气边界的水中产生的激光诱导的球形激波会突破这个边界层，并以椭圆或圆柱形激波的形式在空气中扩散。突破后，激波被加速，在垂直于水面和切向水面的空气中速度不同。在突破表面后，两种激波速度均高于液体中的激波速度。如果击穿的位置在水面以下约0.1毫米处，则激光引起的相对较弱的球形激波会扩散到水空间中，并且也会突破水-气边界。初始球形激波的表面突破在水面上方的空气空间中驱动非球形强激波。几微秒后，空气中激波的速度分量和液体中初始弱激波的速度分量分别以声速传播。因此，如果初始光学击穿仍然发生在液体中，但非常靠近水-空气边界，则液体表面上和液体表面下的动力学过程是非常不同的。液体中的初始球形激波不仅会被传递到空气中，而且会被表层反射。这些稀薄波降低了液体中的压力并干扰了初始的球形激波。球形激波产生后，液体中产生空化泡。本文重点研究了液-气边界表面突破后激波在液-气边界下方和上方的传播。试验液体为蒸馏水。利用两台同步CCD相机，从水面上方和下方同时观测边界层，对该现象进行了研究。
Laser-induced spherical shocks generated in water close to a liquid–air boundary break through this boundary layer and spread out in air as an elliptical or a cylindrical shock wave. After breakthrough, the shock wave is accelerated and its velocity in air is different perpendicular and tangential to the water surface. Immediately after surface breakthrough both shock velocities are higher than the shock velocity in liquid. If the position of the breakdown is about 0.1 mm below the water surface a laser-induced relatively weak spherical shock spreads out into the water space and also breaks through the water–air boundary. The surface breakthrough of the initial spherical shock wave drives a non-spherical strong shock wave in the air space above of the water surface. After some microseconds both velocity components of the shock in air as well as the initial weak shock in liquid propagate with sound velocities, respectively. As a consequence, the dynamical process is very different above and below the liquid surface if the initial optical breakdown occurs still in liquid but very near to the water–air boundary. The initial spherical shock in liquid will not only be transmitted into air but also reflected from the surface layer. Those rarefaction waves decrease the pressure in the liquid and interfere with the initial spherical shock. A cavitation bubble arises in liquid subsequently to the spherical shock wave. In this investigation the propagation of shock waves below and above the boundary liquid–air after surface breakthrough are in focus. The test liquid is distilled water. The phenomena have been studied by observing the boundary layer simultaneously from below and above the water surface with two synchronized CCD cameras.