激光空泡刚性半球面内运动

采用甚高速照相技术与建立激光空泡在刚性半球壁面内的运动模型相结合的方法,确定了激光空泡在刚性半球面壁内的运动特性与无量纲距离的关系,提出了最佳无量纲距离概念。结果表明:半球反射面的半径与激光空泡最大半径之比小于1.1时,激光空泡在第1次膨胀时就会产生严重的变形并弹出半球面,并产生空化泡和空蚀,它们均会严重影响激光声的传播。该比值在1.1~3.3时,激光空泡将在第3次收缩之前接触半球面,容易对壁面造成空蚀。在该比值大于3.3的情况下,激光空泡在第3次收缩之前不会接触半球面,对激光声的传播和反射特性影响较小。如果考虑把空泡第1次溃灭时产生的激光声的声学中心控制在击穿点时,需要把该比值控制在5以上。

Dynamics of laser-induced bubble in rigid half sphere

By the very high speed camera technology and numerical calculation, the relation between dimensionless distance and bubble dynamics in a rigid half sphere is determined. The conception of optimum dimensionless distance is presented, and the conflict between cavitation erosion and utility ratio of sound energy is solved. The result shows that, when the ratio of the half sphere radius to the maximum bubble radius is smaller than 1.1, the laser-induced bubble will jump out of the half sphere in the first expanding, and cavitation may appear. The cavitation bubble and cavitation erosion have adverse effects on the transmission of the laser-induced sound. When the ratio is bigger than 1.1 and smaller than 3.3, the laser induced bubble will meet the half sphere before the third collapsing, which