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Journal of Mechanical Science and Technology 29 (2) (2015) 527~541
www.springerlink.com/content/1738-494x
DOI 10.1007/s12206-015-0113-2
A PIV study of the near wake flow features of a square cylinder: influence of corner radius
R. Ajith Kumar1, Chang Hyun Sohn2,* and B. H. Lakshmana Gowda3
1Department of Mechanical Engineering. AMRITA University, Amritapuri Campus, Kollam District, India
2School of Mechanical Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu, 702-701, Korea
3Department of Mechanical Engineering, BTL Institute of Technology, Bommasandra, Bangalore, India
(Manuscript Received August 28, 2014; Revised October 16, 2014; Accepted October 16, 2014)
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Abstract
In this study, the near wake characteristics of transversely oscillating square-section cylinders with different corner radii were investigated using the particle image velocimetry (PIV) technique in a water channel with turbulence intensity of 6.5%. Five models with r/B = 0, 0.1, 0.2, 0.3, and 0.5, respectively (where r and B represent the corner radius and the characteristic dimension of the body, respectively), were studied, with the body oscillation limited to that under the lock-in condition. Corner radius was found to significantly influence the characteristics of the flow around the bodies, both under stationary and oscillating conditions. The results indicate that the Strouhal number and vortex strength of the flow increase and decrease, respectively, with an increase in the r/B ratio. The spacing between two rows of vortices (b) as well as that between consecutive vortices in a row (a) was also found to decrease with the increase in the corner radius. The b/a ratio was found to be nearly independent of the r/B ratio and body oscillation.
Keywords: Corner radius; Flow-induced vibration; Oscillating square cylinder; PIV; Wake structure
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1. Introduction
The study of flow-induced vibration has emerged as an important branch of fluid mechanics as is evident from pertinent research literature. Flow-induced vibration is observed in many practical areas of engineering, viz., heat exchangers, tubular piles, power cables, and marine and wind engineering structures. Among structural geometries, the circular section appears to be the most widely employed geometry, possibly because of its simplicity. Non-circular sections, particularly square and rectangular sections, are also employed in a variety of applications such as bridges and buildings. However, certain engineering situations instead demand structural geometries that are neither perfectly square nor circular, but square or rectangular sections...