Interaction of circular cylinder wake with a short asymmetrically located downstream plate |
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Authors: | S B Yucel O Cetiner M F Unal |
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Institution: | (1) Department of Aeronautical Engineering, Istanbul Technical University, 34469 Istanbul, Turkey; |
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Abstract: | This study reveals the interaction patterns of separated shear layers from a circular cylinder with a short downstream plate
and their reflection on the frequency and the formation length of the vortices from the cylinder as a function of plate location
relative to the cylinder. The effect of horizontal (G/D) and vertical (Z/D) distances between the cylinder and the plate on the near wake is studied via Digital Particle Image Velocimetry (DPIV) in
a water channel for Reynolds numbers of 200, 400 and 750, based on the cylinder diameter D. It is shown that the interaction of wake with the plate of length D can be categorized depending on the horizontal and the vertical distances between the cylinder and the plate. For the vertical
distance range of Z/D ≤ 0.7, there is a critical horizontal spacing before which the shear layers from the cylinder are inhibited to form vortices
in front of the plate. Resulting elongated recirculation region between the plate and the cylinder suggests modification of
the absolutely unstable near wake of free circular cylinder in favor of convective instability. Z/D = 0.9 provides a passage from Z/D ≤ 0.7 to ≥1.1 and is associated with a dominant effect on the near-wake characteristics of interaction of shear layers from
the cylinder with those from the downstream plate. For Z/D ≥ 1.1, there is again, yet a smaller critical horizontal spacing after which vortices interact with decreased downstream
plate interference. In this vertical separation distance range, a gap flow between the plate and the cylinder plays a determining
role on the formation length and St number of vortices for small horizontal spacing values. |
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