An Experimental Investigation of the Formation and Transition of a Double Eyewall Vortex

• Main Authors: Yi-Che Chiu, 邱奕哲
• Other Authors: Chin-Chou Chu
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/50226878882661191732

碩士 === 國立臺灣大學 === 應用力學研究所 === 98 === In this thesis, the formation and transition process of double eyewall vortices were investigated in a rotating tank with background vorticity. After a quasi-steady bathtub vortex is generated, the vortex is intensified and strengthened caused by a sudden increase and decrease of suction rate. It is observed that the core region of vortex evolves into a transition state, expanding the core radius resultant of the sudden decrease of the suction rate. This is followed by the formation of double eyewall structure identified by the double-peaked velocity distribution in the azimuthal component due to the sudden increase of the suction rate. According to the experimental results, the criterion of formation of double eyewall vortex are with radius ratio rc* > 1 and vorticity ratio ζc* > 4.8. Note that the radius expansion, change of intensity and change of strength are significantly parameters to form the double eyewall structure, which are similar to the results of Kuo et al. (2004). Furthermore, double eyewall phenomea can be also induced by the interaction of topography and nonsymmetrical in-flow. Preliminary results show the phenomenon of the formation of double eyewall structure by towing a topography toward a vortex. Similar experimental results have not been observed in literatures yet. Also, these phenomena are similar to what were observed in typhoon vortices.