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Fundamental Issues and Canonical Flows

Characteristic Flow Field Behind a Square-Cylinder Using Upstream Mesh Fences

[+] Author and Article Information
Shun C. Yen1

Chen W. Yang

Department of Mechanical and Mechatronic Engineering,  National Taiwan Ocean University, Keelung, Taiwan 202, Republic of China

1

Corresponding author.

J. Fluids Eng 134(9), 091202 (Aug 22, 2012) (9 pages) doi:10.1115/1.4004904 History: Received July 09, 2010; Accepted August 15, 2011; Published August 22, 2012; Online August 22, 2012

The flow behaviors around a square cylinder were modulated using the passive mesh fence. The effects of Reynolds number (Re) and rotation angle (θ) on the square-cylinder flow fields using different turbulence intensity (TI) were also investigated. Additionally, various steel mesh fences with different mesh densities were installed between the nozzle outlet and the test-section inlet to adjust the free-stream TI. The Reynolds number and turbulence intensity used in this investigation are 3.0 × 104  ≤ Re ≤ 1.0 × 105 and 0.32% ≤ TI ≤ 0.82%. The flow fields are visualized using the surface oil-flow visualization scheme. Furthermore, the flow patterns are classified as—leading-edge bubble, separation bubble, separation, leading-edge separation, and boundary-layer attached modes. Specifically, the leading-edge bubble mode does not exist while θ and TI are low. Moreover, a hot-wire anemometer was placed in the wake to detect the vortex-shedding frequency. The experimental results indicate that Strouhal number (St) decreases with increasing the free-stream TI while TI < 0.45%. However, St approaches a constant as TI > 0.45%. Furthermore, the surface pressure was detected using a pressure scanner and the drag coefficient (CD ) was obtained using the surface-pressure profile. The experimental results also reveal that CD decreases with increasing the free-stream TI. However, the change rate of CD for TI < 0.45% exceeds that for TI > 0.45%.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 4

Schematic sketches of surface oil-flow patterns

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Figure 7

Variations of (a) Strouhal number (St) versus θ using various TI at Re = 8.0 × 104 , and (b) Strouhal number (St) versus TI using various Reynolds numbers at θ = 0 deg

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Figure 8

Distributions of pressure coefficient (Cp) along the peripheral of square cylinders using various turbulence intensities at Re = 8.0 × 104 for (a) θ = 0 deg, (b) θ = 11 deg, (c) θ = 12 deg, (d) θ = 15 deg, (e) θ = 30 deg, (f) θ = 36 deg, and (g) θ = 45 deg

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Figure 9

Variations of drag coefficient (CD ) and lift coefficient (CL ) versus rotation angle (θ) using various TI while Re = 8.0 × 104

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Figure 2

Variations of free-stream turbulence intensity (TI) versus nondimensional coordinate (x/w) while Re = 8.0 × 104

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Figure 1

Experimental setup

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Figure 3

Surface oil-flow patterns at Re = 8.0 × 104

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Figure 5

Distributions of boundary-layer flow modes

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Figure 6

(a) Variations of instantaneous velocity (u) versus time (t). (b) Distributions of power-spectral-density function versus log f. Re = 1.3 × 104 .

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