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Effects of Flow Patterns on Aerodynamic Forces of a Square Cylinder at Incidence

Published online by Cambridge University Press:  31 August 2011

R. F. Huang  and
B. H. Lin
R. F. Huang*
Affiliation:
Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 10607, R.O.C.
B. H. Lin
Affiliation:
Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 10607, R.O.C.
*
*Professor, corresponding author
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Abstract

The pressure distributions around a square cylinder in a crossflow were experimentally studied in a wind tunnel. The subject of study was conventional, but the results presented new findings. The experiments were performed by using a home-made linear pressure scanner. The ranges of Reynolds number and incidence angle were 2 × 104 - 9.4 × 104 and 0° - 45°, respectively. According to the topological flow patterns, the flows around the square cylinder at incidence showed three characteristic regimes: The subcritical, supercritical, and wedge flows. A critical incidence angle αcri = 15° separated the regimes of subcritical and supercritical modes. The results of current study provided information regarding the effects of the topological flow patterns on surface pressure distribution, drag, and lift characteristics. The pressure distributions, drag, and lift presented different characteristics in different characteristic flow regimes and had close correlations with the flows. At the critical incidence angle 15° which separated the subcritical and supercritical regimes, the surface-averaged pressure coefficient on each face displayed local extreme value—The drag coefficient attained a minimum of 1.6, the lateral force coefficient reached a maximum of 0.9. The appearance of the minimum drag at the critical incidence angle was attributed to the reduction of wake width which was induced by two surface flow phenomena: (1) reattachment of the separated boundary layer on the lateral surface facing windward at the critical incidence angle and (2) flow pattern change on the lateral surface facing leeward.

Keywords

Square cylinderPressure distributionDrag and lift
Type
Articles
Information
Journal of Mechanics , Volume 27 , Issue 3 , September 2011 , pp. 347 - 355
Copyright
Copyright © The Society of Theoretical and Applied Mechanics, R.O.C. 2011

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