| Affiliation: | (1) Department of Mechanical Engineering, Tokyo Denki University, 2–2 Kanda-Nishikicho, Chiyoda-ku, 101-8457 Tokyo, Japan;(2) Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 400 Kusong-dong, Yusong-gu, 305-701 Taejon, South Korea |
| Abstract: | The vortex breakdown phenomenon in a closed cylindrical container with a rotating endwall disk was reproduced. Visualizations were performed to capture the prominent flow characteristics. The locations of the stagnation points of breakdown bubbles and the attendant global flow features were in excellent agreement with the preceding observations. Experiments were also carried out in a differentially-rotating cylindrical container in which the top endwall rotates at a relatively high angular velocity  t, and the bottom endwall and the sidewall rotate at a low angular velocity sb. For a fixed cylinder aspect ratio, and for a given relative rotational Reynolds number based on the angular velocity difference t–sb, the flow behavior is examined as |sb/t| increases. For a co-rotation (sb/t>0), the breakdown bubble is located closer to the bottom endwall disk. However, for a counter-rotation (sb/t<0), the bubble is seen closer to the top endwall disk. For sufficiently large values of sb, the bubble ceases to exist for both cases. |
