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Title: Two-dimensionality of a cantilevered-cylinder wake in the presence of an oscillating upstream cylinder
Authors: Xu, S
Zhou, Y
Tu, J
Issue Date: 2008
Publisher: Academic Press
Source: Journal of fluids and structures, 2008, v. 24, no. 4, p. 467-480 How to cite?
Journal: Journal of fluids and structures 
Abstract: The effect of a longitudinally oscillating cylinder on the two-dimensionality of flow around a downstream cylinder is studied based on a two-point correlation measured using two hot-wires. The oscillation amplitude is A/d=0.472 and the oscillation frequency fe/fs=0.0372 and 0.186, where d is the cylinder diameter and fs the frequency of natural vortex shedding from an isolated stationary cylinder. Three centre-to-centre spacing (L) ratios of the two cylinders were examined, i.e., L/d=1.8, 2.5 and 4.8, representing three typical flow regimes. The experiment was conducted at a Reynolds number (Re) of 5920, based on d and the free-stream velocity. It is found that the spanwise correlation of the flow depends on not only the oscillation but also the flow regimes. At L/d=1.8, the correlation is strongest among the three regimes, but worst in the co-shedding regime (L/d=4.8). The upstream cylinder oscillation improves the spanwise correlation of the flow in the gap of the cylinders, irrespective of regimes, especially for L/d=1.8 and 2.5, but impairs that behind the cylinders for L/d=1.8 and 2.5 due to a change in the flow regime. A theoretical analysis based on the boundary vorticity theory indicates that the oscillation increases the vorticity flux, in particular, in the spanwise direction between the cylinders, resulting in a significantly improved spanwise correlation, though this increase is negligibly small behind the downstream cylinder.
ISSN: 0889-9746
EISSN: 1095-8622
DOI: 10.1016/j.jfluidstructs.2007.10.006
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