Wind and Structures

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Features of the flow over a finite length square prism on a wall at various incidence angles

  • Sohankar, A. (Department of Mechanical Engineering, Isfahan University of Technology) ;
  • Esfeh, M. Kazemi (Department of Mechanical Engineering, Isfahan University of Technology) ;
  • Pourjafari, H. (Department of Mechanical Engineering, Yazd University) ;
  • Alam, Md. Mahbub (Institute for Turbulence-Noise-Vibration Interaction and Control, Shenzhen Graduate School, Harbin Institute of Technology) ;
  • Wang, Longjun (Institute for Turbulence-Noise-Vibration Interaction and Control, Shenzhen Graduate School, Harbin Institute of Technology)
  • Received : 2017.09.18
  • Accepted : 2017.12.09
  • Published : 2018.05.25
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Abstract

Wake characteristics of the flow over a finite square prism at different incidence angles were experimentally investigated using an open-loop wind tunnel. A finite square prism with a width D = 15 mm and a height H = 7D was vertically mounted on a horizontal flat plate. The Reynolds number was varied from $6.5{\times}10^3$ to $28.5{\times}10^3$ and the incidence angle ${\alpha}$ was changed from $0^{\circ}$ to $45^{\circ}$. The ratio of boundary layer thickness to the prism height was about ${\delta}/H=7%$. The time-averaged velocity, turbulence intensity and the vortex shedding frequency were obtained through a single-component hotwire probe. Power spectrum of the streamwise velocity fluctuations revealed that the tip and base vortices shed at the same frequency as that ofspanwise vortices. Furthermore, the results showed that the critical incidence angle corresponding to the maximum Strouhal number and minimum wake width occurs at ${\alpha}_{cr}=15^{\circ}$ which is equal to that reported for an infinite prism. There is a reduction in the size of the wake region along the height of the prism when moving away from the ground plane towards the free end.

Keywords

References

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