出水超空泡的形状与弗劳德数影响的实验研究
Experimental Research on the Shape of Water？？Exit Supercavity and the Effect of Froude Number

潜射导弹/射弹超空泡出水时超空泡与界面的作用机理目前还不完全清楚,而非定常流重力作用下的超空泡形状的描述也需要进一步探讨。为此,进行了水下高速射弹超空泡出水的实验研究,用高速摄影仪拍摄了航行体出水过程中空泡形状变化的图像,测量分析了各种不同头型航行体诱导的空泡尺寸、轮廓和生成溃灭形态的变化规律,并将研究结果与已有的理论公式和半经验公式进行了对比。研究表明,对所研究的工况,Savchenko半经验公式的适用范围可以扩展到空化数小于0？？12;此外,实验测得的超空泡归一化长度亦高于考虑弗劳德数影响的Vasin的理论值,文中采用一系数对该公式进行了修正。实验研究还发现,航行体头型对超空泡的尺寸影响较大,超空泡与自由液面接触后,空泡直径有一定程度的增大。
The interreaction mechanism between the supercavitation and the free interface of the submarine？？launched missiles or projectiles with supercavities has not been clearly understood. And the description about the supercavity shape in an unsteady flow with gravity also needs to be further investigated. An experimental study on underwater high？？speed projectiles was carried out in a self？？designed experimental facility. The water？？exit process of projectiles and the shape change of supercavities were recorded by a high？？speed camera. The size, contour, formation and collapse of the supercavities were measured and analyzed. The experiment data were compared with the theoretical formula and semi？？empirical formula. The results show that under the studied conditions, the semi？？empirical formula of Savchenko can be extended to the cavitation number less than 0？？12. In addition, the experimental data are higher than the theoretical value given by Vasin considering the effect of gravity. A coefficient is added to modify the given formula. Furthermore, the experimental study shows that the shape of projectile head has great effect on the size of the formed supercavities. When the supercavities come into contact with the free surface, the supercavity diameter will be increased to a certain extent