中文摘要：

研究自由液面附近空化泡的溃灭特性对认识水利水电工程中的空蚀破坏机理具有重要意义。为进一步认识自由液面附近空化泡的溃灭特性,开展了电火花激发空化泡试验。结果表明：（1）空化泡与自由液面距离较近时总是背离自由液面溃灭,背离的临界条件为空化泡与自由液面的距离约是空化泡最大半径的5倍。空化泡尺寸越大或空化泡与自由液面距离越近,其背离现象越明显。（2）自由液面附近双空化泡相向溃灭融合,且融合体背离自由液面移动。（3）在自由液面和空气泡的共同影响下,空化泡的溃灭方向是二者分别对空化泡作用的矢量和。通过本文研究,对自由液面附近空化泡的溃灭有了定量认识,可以在一定条件下预测空化泡的溃灭方向。

英文摘要：

Study of collapse characteristics of the cavitation bubble near free surface has important signifi- cance in knowing cavitation erosion mechanism in water conservancy and hydropower project. To further un- derstanding collapse characteristics of the cavitation bubble near free surface, experiments the spark-in- duced cavitation bubbles were carried out and the results show that： （1） Cavitation bubbles near free sur- face always deviate from the free surface when collapsing, the critical condition of deviating from the free surface is that the distance between the cavitation bubble and the free surface is about five times of the maximum radius of the cavitation bubble. The larger the size of the cavitation bubble or the closer the cavi- tation bubble away from the free surface, the more obvious the phenomenon will be. （2） Double cavitation bubbles near free surface collapse towards each other and fuse together and the fusion body deviates from the free surface. （3） Under the influence of the free surface and the air bubble, the direction of collapse of the cavitation bubble is vector sum of the respective effect of the free surface and the air bubble. A quantitative knowledge of cavitation bubbles near free surface was developed in this study and collapse di- rections of cavitation bubbles could be predicted under certain conditions.