The vertical water-entry processes of a hollow cylinder with three different velocities are investigated both numerically and experimentally. Three different closure patterns and flow characteristics of the air-entraining cavities induced by water-entry processes are discovered and discussed. Our results show that three different closure patterns appear with the increase of entry velocity, the deep-closure, the surface closure on the through-hole jet and on the geometry wall. Three high-speed regions also appear during the water entry process and their characteristics are different with various closure patterns. Besides, with the increase of water entry velocity, the velocity variation will vary from increase to decrease, but their water depths all increase linearly due to the short time and small variations of velocities.

数值和实验研究了具有三种不同速度的空心圆柱体的垂直入水过程。发现并讨论了水进入过程引起的引气腔的三种不同的闭合方式和流动特性。我们的结果表明，随着进入速度，深层封闭，通孔射流和几何壁表面封闭的增加，出现了三种不同的封闭方式。在入水过程中还会出现三个高速区域，它们的特征因各种关闭方式而不同。此外，随着入水速度的增加，速度的变化会从增大到减小变化，但由于时间短，速度变化小，它们的水深都呈线性增加。