Experimental Study on Vortex Growth during the Early Development of Rotating Disks

In previous studies, the effects of radial clearance on the flow of a rotating disk in a cylindrical vessel have been investigated by using rotating disks of different shapes. As a result, different flow phases were observed in each disk due to the difference in disk dimensions. In this study, we focus on the end-face effect and conduct experiments to visualize the vortex growth process and elucidate the generation mechanism of the vortex structure. From the experiment results, at Re = 4000, 7000, and 9000, four types of vortex flow modes appeared in the vortex development process. However, at Re = 4000, only regular 2-cells and regular 4-cells appeared, and at Re = 9000, only mutated 2-cells and mutated 3-cells appeared. In addition, it was found that only one type appeared depending on the rotational ascent time t_s. When Re = 4000, the rotational ascent time t_s = 0, 2, 7, and 8 was stable at regular 4-cells, while the others were finally stable in regular 2-cells. This study revealed the influence of the acceleration of the rotating disk on the non-unique flows in the cylindrical casing.