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Drag reduction of square cylinders with cut-corners at the front edges

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Abstract

Flow around square cylinders with cut-corners at the front edges is investigated using particle image velocimetry. It is found that drag reduction can be achieved for the tested cut-corner dimensions. The mechanism for the drag reduction is explored on the statistical and structural aspects of the flow. After cutting the corners, the fluctuation intensity of the wake is weakened, the length of the recirculation region behind the square cylinder is increased, while the width of the wake decreases. It is found that the drag coefficient is proportional to the minimum wake width, and the Strouhal number St is inversely proportional to the minimum wake width. It is revealed that the reduced wake width is due to the suppressed separation over the side surfaces for the cylinders with cut-corners at the front edges. On the structural aspect, the phase-averaged flow field and the modes from proper orthogonal decomposition both indicate a decrease in the wake vortex size. A statistical analysis of instantaneous vortices based on Oseen vortex fit reveals that not only the size of the vortex is reduced, but also the strength is weakened.

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Acknowledgments

This work was supported by the National Natural Science Foundation of China with Grant No. 10832001 and No. 11327202.

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Authors and Affiliations

  1. Fluid Mechanics Key Laboratory of Education Ministry, Beijing University of Aeronautics and Astronautics, Beijing, 100191, China

    Guo Sheng He, Nian Li & Jin Jun Wang

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  1. Guo Sheng He
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  2. Nian Li
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  3. Jin Jun Wang
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Correspondence to Jin Jun Wang.

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He, G.S., Li, N. & Wang, J.J. Drag reduction of square cylinders with cut-corners at the front edges. Exp Fluids 55, 1745 (2014). https://doi.org/10.1007/s00348-014-1745-1

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  • DOI: https://doi.org/10.1007/s00348-014-1745-1

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