Wind and Structures Volume 26, Number 5, May 2018, pages 293304
DOI: http://dx.doi.org/10.12989/was.2018.26.5.293  
Flow structures around rectangular cylinder in the vicinity of a wall  
J.F. Derakhshandeh and Md. Mahbub Alam


Abstract [Full Text]  
A numerical study is conducted on the flow characteristics of a rectangular cylinder (chordtowidth ratio C/W = 2  10) mounted close to a rigid wall at gaptowidth ratios G/W = 0.25  6.25. The effects of G/W and C/W on the Strouhal number, vortex structure, and timemean drag and lift forces are examined. The results reveal that both G/W and C/W have strong influences on vortex structure, which significantly affects the forces on the cylinder. An increase in G/W leads to four different flow regimes, namely no vortex street flow (G/W < 0.75), singlerow vortex street flow (0.75< G/W < 1.25), inverted tworow vortex street flow (1.25 < G/W < 2.5), and tworow vortex street flow (G/W > 2.5). Both Strouhal number and timemean drag are more sensitive to C/W than to G/W. For a given G/W, Strouhal number grows with C/W while timemean drag decays with C/W, the growth and decay being large between C/W = 2 and 4. The timemean drag is largest in the singlerow vortex street regime, contributed by a large pressure on the front surface, regardless of C/W. A higher C/W, in general, leads to a higher timemean lift. The maximum timemean lift occurs for C/W = 10 at G/W = 0.75, while the minimum timemean lift appears for C/W = 2 at the same G/W. The impact of C/W on the timemean lift is more substantial in singlerow vortex regime. The effect of G/W on the timemean lift is larger at a larger C/W.  
Key Words  
boundary layers; rectangular cylinder; Strouhal number; vortex shedding frequency  
Address  
J.F. Derakhshandeh: School of Mechanical Engineering of University of Adelaide, Australia Md. Mahbub Alam: Institute for TurbulenceNoiseVibration Interaction and Control, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055, China  