Entrainment and transport of air bubbles by vortex ring

实验研究了涡环对气泡的夹带和输运。涡环发射器由气缸和活塞组成，安装在水箱底部。气缸直径D0和活塞行程L0分别为42.5 mm和100 mm。发射的涡环为层流型，环量小于20000。气泡从连接在气缸表面的针注入涡流环。气泡平均直径为3.2 mm。根据涡环强度和气泡流量对气泡相对于涡环的运动进行了分类。当涡环强度较小时，气泡受涡环的影响较小。随着强度的增加，气泡被有利地卷进涡环。夹带气泡分布在涡核中心附近。当涡环强度较大时，它们由涡环输送。卷吸气泡几乎不改变涡环的对流。涡环的半径在多个气泡夹带的位置变大。

The entrainment and transport of air bubbles by a vortex ring are experimentally investigated. A vortex ring launcher, composed of a cylinder and a piston, is mounted on the bottom of a water tank. The cylinder diameter D0 and the piston stroke L0 are 42.5 mm and 100 mm respectively. The launched vortex ring, of which circulation is less than 20000, is of a laminar type. Air bubbles are injected from a needle, which is attached on the cylinder surface, into the vortex ring. The mean bubble diameter is 3.2 mm. The bubble motions relative to the vortex ring are found to be classified according to the strength of the vortex ring and the bubble flow rate. When the strength of the vortex ring is low, the bubbles are less affected by the vortex ring. With increasing the strength, the bubbles are favorably entrained into the vortex ring. The entrained bubbles distribute around the center of the vortex core. They are transported by the vortex ring when the strength of the vortex ring is large. The entrained bubbles hardly change the convection of the vortex ring. The radius of the vortex ring becomes larger at the position where a number of bubbles are entrained.