Dependence of Strouhal Number, Drag and Lift on the Ratio of Cylinder Diameters in a Two-Tandem Cylinder Wake

Alam, Mahbub and Zhou, Y. (2007). Dependence of Strouhal Number, Drag and Lift on the Ratio of Cylinder Diameters in a Two-Tandem Cylinder Wake. In: Peter Jacobs, Tim McIntyre, Matthew Cleary, David Buttsworth, David Mee, Rose Clements, Richard Morgan and Charles Lemckert, 16th Australasian Fluid Mechanics Conference (AFMC). 16th Australasian Fluid Mechanics Conference (AFMC), Gold Coast, Queensland, Australia, (750-757). 3-7 December, 2007.

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Author Alam, Mahbub
Zhou, Y.
Title of paper Dependence of Strouhal Number, Drag and Lift on the Ratio of Cylinder Diameters in a Two-Tandem Cylinder Wake
Conference name 16th Australasian Fluid Mechanics Conference (AFMC)
Conference location Gold Coast, Queensland, Australia
Conference dates 3-7 December, 2007
Proceedings title 16th Australasian Fluid Mechanics Conference (AFMC)
Place of Publication Brisbane, Australia
Publisher School of Engineering, The University of Queensland
Publication Year 2007
Year available 2007
Sub-type Fully published paper
ISBN 978-1-864998-94-8
Editor Peter Jacobs
Tim McIntyre
Matthew Cleary
David Buttsworth
David Mee
Rose Clements
Richard Morgan
Charles Lemckert
Start page 750
End page 757
Total pages 8
Collection year 2007
Language eng
Abstract/Summary This paper presents the effect of the diameter of a cylinder and Reynolds number (Re) on time-averaged drag (CD), rms drag (CDrms), rms lift (CLrms) and Strouhal number (St) in the wake of a downstream cylinder. The Re range considered is 7×103 ~ 3.3×104. The upstream cylinder diameter d investigated was 6, 10, 15, 20 and 25 mm, while the downstream cylinder diameter D was 25 mm, corresponding to d/D ranging from 0.24 ~ 1.0. The spacing ratio L/d (where L is the distance between the center of the upstream cylinder center and the leading stagnation point of the downstream cylinder) is 1, 2 and 5.5, covering different flow regimes. At L/d = 1, d/D = 1.0, increasing Re results a switching of a steady-reattachment to alternating-reattachment of the two free shear layers of the upstream cylinder on the downstream cylinder at Re = 23250, augmenting the width between the two free shear layers in the gap between the cylinders. As decreasing d/D corresponds to diminishing width between the free shear layers in the gap, the steady-reattachment of the shear layers occurred for d/D < 1.0 at L/d = 1 and for d/D < 0.8 at L/d = 2. While increasing d/D from 0.24 to 1.0 at L/d = 5.5 changes St from 0.203 to 0.12, that at L/d = 1 and 2 has little or no influence on St. An augmentation of d/D from 0 (isolated cylinder) progressively to 0.24, 0.4, 0.6 to 0.8 causes a reduction in CD by about 12~15%, 24~30%, 67~72% and 87~94% at L/d = 1 and 6~20%, 36~38%, 73~77% and 86~91% at L/d = 2, respectively. As d/D grows from 0.24 to 1.0, CD at L/d = 1 and 2 decays faster with d/D than at L/d = 5.5. d/D = 0.24~0.6 in the reattachment regime (i.e., at L/d =1 and 2) may generate streamwise vibration of the cylinder at fv/fn1 ≈ 0.5 and 1, in addition to at fv/fn1 = 2, where fv and fn1 are the vortex-shedding and first-modenatural frequencies of the cylinder. At L/d = 5.5, CDrms and CLrms grow with d/D. On the other hand, at L/d = 1 and 2, CDrms is more or less constant and CLrms diminishes with d/D.
Subjects 290000 Engineering and Technology
Keyword time-averaged drag
downstream cylinder
trouhal number
Q-Index Code E1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Conference Paper
Collection: 16th Australasian Fluid Mechanics Conference
 
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Created: Wed, 19 Dec 2007, 14:59:38 EST by Thelma Whitbourne on behalf of School of Engineering