Numerical and Experimental Investigation of Interactions between Taylor Wall and Rotating Cylinder in a Rotating Fluid

• Main Authors: Kuan-Ruei Lai, 賴冠叡
• Other Authors: Chien-Cheng Chang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/68073486754267110398

碩士 === 國立臺灣大學 === 應用力學研究所 === 102 === ABSTRACT There are lots of exciting phenomenon in rotating fluids, and the critical role which Coriolis force play is the most fascinating. The aim of this study is to investigate the interactions between two flow structures among vortices with numerical analysis and experimental measurements. The first one is the bathtub vortex driven by a drain-source under rotating background vorticity, which vortex structure is similar to that of typhoon; the other is the Taylor column, which is a topography effect that forms closed-loop flow field above terrain structures under rotating background. Both rotating flows mentioned above has long been studied broadly in the literature, but the work of studying their interactions has just recently began in our laboratory. In the previous study, the tub model has a tiny drain hole located at the center of bottom wall to generate bathtub vortex; and a cylinder is fixed on the center of top wall to induce Taylor column effect, which indeed leads to a new discovery. In addition to the Ekman layer on surfaces of solid boundary and its upwelling behavior, our team have determined the multi-layered vortex structure between the cylinder and drain hole. Moreover, the existence of Taylor wall and a strong Taylor upwelling that climbs along outside of Taylor wall has first been confirmed. This study is an extension of previous work, which consider the cylinder and its corresponding vertical projection area on the bottom wall rotating asynchronously to the background rotation. Steady-state solution of Navier-Stokes equation is solved under the rotating reference frame with finite volume method analysis software ANSYS Fluent, and some significant parameters for discussions are the height ratio of cylinder to distance between top and bottom walls (h/H), which are 0.3, 0.5, 0.7 and without cylinder as contrast; and the angular velocity ratio of cylinder and its corresponding area on the bottom wall to background rotation (ω/&;#8486;), which ranges from -8/3 to 8/3. On the other hand, streak line patterns and flow field velocity profiles are measured using fluorescent dye visualization and Particle Image Velocimetry (PIV) in the experiment. The results show that along with the increasing angular velocity of cylinder, when it rotates in the same direction as the rotating tub, the Taylor wall radially expands and its height and width increases; when the cylinder rotates in the opposite direction, the Taylor wall contracts and its height and width reduces.