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Wind and Structures
  Volume 19, Number 4, October 2014, pages 389-404
DOI: http://dx.doi.org/10.12989/was.2014.19.4.389
 


Flow control downstream of a circular cylinder by a permeable cylinder in deep water
Bengi Gozmen and Huseyin Akilli

 
Abstract
    The flow characteristics of a circular cylinder surrounded by an outer permeable cylinder were experimentally investigated using Particle Image Velocimetry Technique in deep water flow. In order to consider the effects of diameter and porosity of the outer cylinder on flow structures of the inner cylinder, five different outer cylinder diameters (D=37.5, 52.5, 60, 75 and 90 mm) and eight different porosities (B= 0.4, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8 and 0.85) were selected. During the experiments, the diameter of inner cylinder was kept constant as d=30 mm. The depth-averaged free-stream velocity was adjusted as U=0.156 m/s, which corresponds to the Reynolds number of Re=5000 based on the inner cylinder diameter. It has been concluded that both the outer permeable cylinder diameter and the porosity have important influences on the attenuation of vortex shedding in the wake region. The presence of outer permeable cylinder decreases the magnitude of Reynolds shear stress and turbulent kinetic energy compared to the bare cylinder case. Moreover, the spectral analysis of vortex shedding frequency has revealed that the dominant frequency of vortex shedding downstream of the cylinder arrangement also reduces substantially due to the weakened Karman shear layer instability.
 
Key Words
    passive control; PIV; circular cylinder; vortex shedding
 
Address
Bengi Gozmen: Department of Mechanical Engineering, Usak University, 1 Eylül Kampüsü, 64200, Usak, Turkey
Huseyin Akilli:Department of Mechanical Engineering, Cukurova University, 01330, Yüreğir, Adana, Turkey
 

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