Abstract Recent theoretical and numerical studies predict the Moffatt eddies near the interface-wall intersection in a two-fluid flow. The current work provides the first experimental evidence of this phenomenon of fundamental interest. It also reveals a jump of the azimuthal velocity at the interface which can be important for vortex bioreactors. The rotating lid drives a two-fluid flow in a vertical cylindrical container whose other walls are stationary. Near the lid, the centrifugal force pushes the upper fluid to the sidewall thus developing its centrifugal meridional circulation. This motion drives the bulk counter-circulation and the Moffatt eddies in the lower fluid at a slow rotation. Using sunflower oil for the upper fluid, water-glycerin or alcohol-glycerin solutions for the lower fluid, and assemble averaging of PIV images allow for velocity measurement and flow visualization even in a creeping motion. This advanced experimental technique helps detect velocity jumps, occurring at the interface and the Moffatt outermost eddy.

中文翻译：

---

两种流体涡流中的速度跳跃和莫法特涡流

摘要 最近的理论和数值研究预测了两流体流动中界面-壁交叉点附近的莫法特涡流。目前的工作提供了这种具有根本意义的现象的第一个实验证据。它还揭示了界面处方位角速度的跳跃，这对于涡流生物反应器可能很重要。旋转盖在其他壁静止的垂直圆柱形容器中驱动两种流体流动。在盖子附近，离心力将上部流体推向侧壁，从而形成其离心经向循环。这种运动驱动了下部流体中的大量反循环和莫法特涡流以缓慢旋转。上液使用葵花籽油，下液使用水-甘油或酒精-甘油溶液，并组装 PIV 图像的平均值，即使在爬行运动中也可以进行速度测量和流量可视化。这种先进的实验技术有助于检测发生在界面和莫法特最外层涡流处的速度跳跃。