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Wind and Structures
  Volume 14, Number 1, January 2011, pages 35-53
DOI: http://dx.doi.org/10.12989/was.2011.14.1.035
 


Advancing drag crisis of a sphere via the manipulation of integral length scale
Niloofar Moradian, David S-K. Ting and Shaohong Cheng

 
Abstract
    Spherical object in wind is a common scenario in daily life and engineering practice. The main challenge in understanding the aerodynamics in turbulent wind lies in the multi-aspect of turbulence. This paper presents a wind tunnel study, which focuses on the role of turbulence integral length scale on the drag of a sphere. Particular turbulent flow conditions were achieved via the proper combination of wind speed, orifice perforated plate, sphere diameter (D) and distance downstream from the plate. The drag was measured in turbulent flow with and turbulence intensity Tu up to 6.3%. Our results confirmed the general trends of decreasing drag coefficient and critical Reynolds number with increasing turbulence intensity. More interestingly, the unique role of the relative integral length scale has been revealed. Over the range of conditions studied, an integral length of approximately 65% the sphere diameter is most effective in reducing the drag.
 
Key Words
    sphere; orifice perforated plate; turbulence; drag coefficient; integral length scale.
 
Address
Niloofar Moradian: Department of Mechanical, Automotive and Materials Engineering, University of Windsor, 401 Sunset Avenue, Windsor, ON, Canada N9B 3P4
David S-K. Ting: Department of Mechanical, Automotive and Materials Engineering, University of Windsor, 401 Sunset Avenue, Windsor, ON, Canada N9B 3P4
Shaohong Cheng: Department of Civil and Environmental Engineering, University of Windsor,401 Sunset Avenue, Windsor, ON, Canada N9B 3P4
 

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