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Sixth International Symposium on Turbulence and Shear Flow Phenomena
June, 22-24, 2009 , Seoul National University, Seoul, Korea

DOI: 10.1615/TSFP6

FLOW FIELD CHARACTERISTICS OF CIRCULAR-CYLINDER WAKE WITH A NEAR-WAKE WIRE DISTURBANCE

pages 251-256
DOI: 10.1615/TSFP6.400
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ABSTRAKT

The 3-D transition of the flow behind a circular cylinder with a near-wake wire disturbance has been investigated experimentally. The presence of a wire in the near-wake region of the cylinder causes an unnatural mode of shedding to occur, namely Mode C. Cross-stream plane flow visualization and PIV experiments are done to investigate the influence of the wire on various properties of the flow, such as the dynamics of the spanwise structures. Experiments were performed at Reynolds numbers of Re = 185, 215. From these experiments it can be concluded that the Mode C structures are formed as secondary streamwise vortices around the primary von Karman vortices. The spanwise wavelength of those Mode C structures is determined in the near wake of the cylinder and is approximately 2.2 cylinder diameters. The presence of the wire also triggered the occurrence of period doubling in the wake. Mode C structures shift half the wavelength of the 3-D structures within each shedding cycle, i.e. practically doubling the shedding period. Neither in the natural shedding modes, Mode A and Mode B, nor in forced shedding Mode E this phenomenon is observed.

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