Determination of flow configurations and fluid forces acting on two staggered circular cylinders of equal diameter in cross-flow

Alam, Md. Mahbub; Sakamoto, Hiroshi; Zhou, Yu

doi:10.1016/j.jfluidstructs.2005.07.009

Cited by 86 publications

(31 citation statements)

References 52 publications

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“…It is well known that at a moderate P ‫ء‬ , the downstream cylinder acts to divert the gap flow toward the wake centerline of the upstream cylinder, resulting in the wide wake of lower St behind the downstream cylinder and a narrow wake of higher St behind the upstream cylinder. 2,4,5,20,26 For the present Re range, the boundary layer over the upstream cylinder becomes thinner with increasing Re and the separation point shifts upstream toward the forward stagnation point, 25 implying an increased separation angle. With an adequate upstream shift at Re Ͼ Re c , the inner shear layer, separated from the upstream cylinder, reattaches on the downstream cylinder; part of it separates from the gap side, generating a shear-layerreattachment flow that forms a small gap flow ͓Fig.…”

Section: Typementioning

confidence: 89%

“…15͑a͒ to the other ͓Fig. 15͑b͔͒ is discontinuous, 13,26 resulting in the rather abrupt collapse of the two St values into about 0.19 ͓Fig. 14͑b͔͒.…”

Section: Typementioning

confidence: 98%

“…Due to a small P ‫ء‬ , part of the bifurcated flow may bounce back to the upstream cylinder, forming a separation bubble on the upstream cylinder. 26 The bubble has a great impact on the upstream cylinder lift but not on St ͑Refs. 8 and 26͒ as the outer shear layers of the two cylinders alternately form vortices.…”

Section: Phys Fluids 21 125105 ͑2009͒mentioning

confidence: 99%

“…15͑a͔͒. The outer shear layer separated from the upstream cylinder forms vortices at the higher St, while the shear layers over the downstream cylinder form vortices at the lower St. 2,8,26 As advected downstream, the vortices of the higher value of St interact with those of the lower St, producing a single combined street of the lower St. Since the vortex formation length reduces from Re= 3.0ϫ 10 3 to 2 ϫ 10 4 , the shear layer separated from the inner side of the upstream cylinder may roll up to form vortices before reaching the downstream cylinder, producing a coshedding flow ͓Fig.…”

Section: Typementioning

confidence: 99%

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Reynolds number effect on the wake of two staggered cylinders

et al. 2009

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This work aims to investigate, based on the measured/reported Strouhal number ͑St͒ and the flow structure, the Reynolds number ͑Re͒ effect on the wake of two identical cylinders with a diameter of d over P ‫ء‬ = P / d = 1.2-4.0 and ␣ = 0°-90°, where P is the center-to-center spacing between the two cylinders and ␣ is the angle of incident flow with respect to the line through the two cylinder centers. The Re range examined is from 1.5ϫ 10 3 to 2.0ϫ 10 4 . Two hotwires were used to measure St simultaneously behind each of the two cylinders. The St-Re relationship is classified into four distinct types, i.e., types 1-4. Each is linked to distinct initial conditions, viz., interactions between the four shear layers around the cylinders. Type 1 occurs at small P ‫ء‬ , not exceeding 1.25. The two cylinders act like a single body, producing a single St across the wake throughout the range of Re examined. On the other hand, type 2 occurs at small ␣ ͑Ͻ10°͒. Although single valued, the St in type 2 displays a sudden jump with increasing Re due to a switch in the shear layer, separated from the upstream cylinder, from overshooting to reattachment on the downstream cylinder ͑type 2A͒ or from reattachment to coshedding vortices ͑type 2B͒, depending on P ‫ء‬ . Type 3 is in the region of intermediate P ‫ء‬ ͓͑1.2-1.5͒-2.2͔ and ␣ ͑10°-75°͒. Two distinct St occur at low Re. The lower and the higher ranges of St are associated with the downstream and upstream cylinders, respectively. With increasing Re, the higher St collapses to the lower, which is attributed to a change in the inner shear layer, separated from the upstream cylinder, from squeezing through the gap between cylinders to reattachment on the downstream cylinder. Type 4 occurs at large P ‫ء‬ ͑Ͼ1.2-2.2͒ and again exhibits at low Re two St, above and below the Strouhal number St 0 in the wake of an isolated cylinder, both changing suddenly or progressively to St 0 with increasing Re, which results from a change in the inner shear layer, separated from the upstream cylinder, from reattachment on the downstream cylinder to forming vortices between the cylinders. These types of Re-St relationships are also connected to the flow structure modes reported in literature. The dependence of the St and St-Re relationships on P ‫ء‬ and ␣ is provided, which may be used for the prediction of St in related problems.

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Section: Typementioning

confidence: 89%

“…15͑a͒ to the other ͓Fig. 15͑b͔͒ is discontinuous, 13,26 resulting in the rather abrupt collapse of the two St values into about 0.19 ͓Fig. 14͑b͔͒.…”

Section: Typementioning

confidence: 98%

Section: Phys Fluids 21 125105 ͑2009͒mentioning

confidence: 99%

Section: Typementioning

confidence: 99%

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Reynolds number effect on the wake of two staggered cylinders

et al. 2009

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“…Only a few studies have reported force measurements for the upstream cylinder [2,5,6]. Furthermore, fluctuating force measurements in the literature are very scant, though the fluctuating lift and drag forces acting on structures are major causes of the fatigue failure of the structures and are used for predicting flow-induced responses.…”

Section: Introductionmentioning

confidence: 99%

Wind-load, pressure and velocity measurements: post processing and discussion

Alam

2014

EPJ Web of Conferences

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Abstract. Because of the practical importance of bluff bodies subjected fluid flow, fluid dynamics around two-dimensional bluff bodies, especially circular cylinders, has been studied in light of three major parameters, namely flow-induced force, surface pressure and wake. Though all the three are interrelated, the first two are the integrated behavior of flow velocity around the cylinder. Thus measurements of flowinduced forces, surface pressures and velocity fields are very important in the engineering discipline. This paper discusses force and pressure measurement results for two circular cylinders at gap-spacing ratio T/D varied from 0.1 to 5 and the attack angle α from 0° to 180° where T is the gap width between the cylinders and D is the diameter of a cylinder. Post processing of pressure and force signals is also elaborated.

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