Wake flow behaviour behind a smaller cylinder oscillating in the wake of an upstream stationary cylinder

The flow patterns around a cylinder oscillating freely in the wake of a larger cylinder upstream were investigated using the particle image velocimetry technique. The upstream cylinder was fixed at both ends while the downstream smaller cylinder was held by springs such that it was free to oscillate...

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Bibliographic Details
Main Authors: Gao, Yangyang, Sun, Zhilin, Tan, Danielle S, Yu, Dingyong, Tan, Soon Keat
Other Authors: DHI-NTU Centre
Format: Article
Language:English
Published: 2014
Subjects:
Online Access:https://hdl.handle.net/10356/105862
http://hdl.handle.net/10220/20927
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Institution: Nanyang Technological University
Language: English
Description
Summary:The flow patterns around a cylinder oscillating freely in the wake of a larger cylinder upstream were investigated using the particle image velocimetry technique. The upstream cylinder was fixed at both ends while the downstream smaller cylinder was held by springs such that it was free to oscillate in the transverse direction. The flow patterns, amplitudes of oscillation and vortex shedding frequencies were compared with those of a single cylinder. In the presence of the upstream cylinder, the three parameters characterizing the oscillation response of the smaller cylinder—amplitude of oscillation, vortex shedding frequency and Reynolds stresses—were greatly reduced. While their magnitude increased with gap ratio, these three parameters were still smaller than the corresponding magnitudes for a single oscillating cylinder. The peak values of turbulence statistics such as Reynolds shear stress and normal stress behind the oscillating downstream cylinder were similarly reduced, and increased with gap ratios.