Control of vortex shedding from circular cylinder by acoustic excitation

Title & Authors
Control of vortex shedding from circular cylinder by acoustic excitation
Kim, Gyeong-Cheon; Bu, Jeong-Suk; Lee, Sang-Uk; Gu, Myeong-Seop;

Abstract
The flow around a circular cylinder was controlled by an acoustic excitation issued from a thin slit along the cylinder axis. The static pressure distributions around the cylinder wall and flow characteristics in the near wake have been measured. Experiments were performed under three cases of Reynolds number, 7.8 * 10$\small{\^}$4/, 2.3 * 10$\small{\^}$5/ and 3.8 * 10$\small{\^}$5/. The effects of excitation frequency, sound pressure level and the location of the slit were examined. Data indicate that the excitation frequency and the slit location are the key parameters for controlling the separated flow. At Re$\small{\_}$d/, = 7.8 * 10$\small{\^}$4/, the drag is reduced and the lift is generated to upward direction, however, at Re$\small{\_}$d/, =2.3 * 10$\small{\^}$5/ and 3.8 * 10$\small{\_}$5/, the drag is increased and lift is generated to downward direction inversely. It is thought that the lift switching phenomenon is due to the different separation point of upper surface and lower surface on circular cylinder with respect to the flow regime which depends on the Reynolds number. Vortex shedding frequencies are different at upper side and lower side. Time-averaged velocity field shows that mean velocity vector and the points of maximum intensities are inclined to downward direction at Re$\small{\_}$d/ = 7.8 * 10$\small{\^}$4/, but are inclined to upward direction at Re$\small{\_}$d/ = 2.3 * 10$\small{\^}$5/.
Keywords
Acoustic Exitation;Control of Vortex Shedding;Pressure Coefficient;Drag Coeffieicnt;Lift Coefficient;
Language
Korean
Cited by
1.
Groove에 의한 원주 후류의 유동구조 변화,서성호;홍철현;부정숙;

한국마린엔지니어링학회지, 2008. vol.32. 6, pp.901-907
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