Vortex Shedding From Two Circular Cylinders in Staggered Arrangement

Kiya, Masaru; Arie, Mikio; Tamura, Hisataka; Mori, Hiroshi

doi:10.1115/1.3240637

Cited by 122 publications

(48 citation statements)

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“…The observations imply less quasi-periodic vortex shedding in Mode S-Ib than in Mode S-Ia, consistent with previous reports. Kiya et al (1980) observed weak vortex shedding from two staggered cylinders at P * 6 2.5 and α < 20 • . See region 2 in their figure 9.…”

Section: Mode S-ibmentioning

confidence: 85%

“…A thin laser sheet, which was generated by laser beam sweeping, vertically illuminated the flow field at the mid-plane of the working section. The laser beam was produced by a Spectra-Physics Stabilite 2017 argon ion laser source with a maximum power output of 4 W. A digital video camera recorder (Sony Kiya et al (1980) at Re = 15 800; ᭢, Sumner et al (2000) at Re = 1350; ᭹, Alam & Sakamoto (2005) at Re = 55 000; ᭜ Sumner et al (2005) at Re = 50 000 are included for comparison. ᮀ, present data.…”

Section: Methodsmentioning

confidence: 99%

“…At such a small spacing, the two cylinders behave like one body (Kiya et al 1980;Sumner et al 2000) and shear-layer separation occurs only from the free-stream sides of the cylinder pair, resulting in one frequency of vortex shedding (see figure 4 of Sumner et al 2000). St progressively decreases from about 0.2 to 0.09 as α varies from 0 • to 90 • .…”

Section: Strouhal Numbersmentioning

confidence: 99%

“…Numerous investigations have been made previously on St (table 1). Kiya et al (1980) was perhaps the first to report two different St behind two staggered cylinders at large P and α, with the one generated by the upstream cylinder higher than that by the downstream. However, their map of St was incomplete, with the higher St missing in some cases (Alam & Sakamoto 2005).…”

Section: Introductionmentioning

confidence: 99%

“…Another classification is based on vortex shedding frequencies, f s , in the wake. Kiya et al (1980) measured f s for P /d = 1.0 ∼ 5.5, α = 0 • ∼ 180 • with an interval of 15 • (Re = 1.58 × 10 4 ), and classified the flow into five regions, depending on whether St was greater or smaller than that in an isolated cylinder wake, and whether vortex shedding from the upstream cylinder occurred. The five regions are characterized by bistable vortex shedding, weak (or no) vortex shedding, St larger and smaller than that in an isolated cylinder wake, and single-body-like vortex shedding, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Flow structure behind two staggered circular cylinders. Part 1. Downstream evolution and classification

Zhou

2008

J. Fluid Mech.

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Flow structures, Strouhal numbers and their downstream evolutions in the wake of two-staggered circular cylinders are investigated at Re = 7000 using hot-wire, flowvisualization and particle-image velocimetry techniques. The cylinder centre-to-centre pitch, P , ranges from 1.2d to 4.0d (d is the cylinder diameter) and the angle (α) between the incident flow and the line through the cylinder centres is 0 • ∼ 90 • . Four distinct flow structures are identified at x/d > 10 (x is the downstream distance from the mid-point between the cylinders), i.e. two single-street modes (S-I and S-II) and two twin-street modes (T-I and T-II), based on Strouhal numbers, flow topology and their downstream evolution. Mode S-I is further divided into two different types, i.e. SIa and S-Ib, in view of their distinct vortex strengths. Mode S-Ia occurs at P /d 6 1.2. The pair of cylinders behaves like one single body, and shear layers separated from the free-stream sides of the cylinders roll up, forming one street of alternately arranged vortices. The street is comparable to that behind an isolated cylinder in terms of the topology and strength of vortices. Mode S-Ib occurs at α 6 10 • and P /d > 1.5. Shear layers separated from the upstream cylinder reattach on or roll up to form vortices before reaching the downstream cylinder, resulting in postponed flow separation from the downstream cylinder. A single vortex street thus formed is characterized by significantly weakened vortices, compared with Mode S-Ia. Mode S-II is identified at P /d = 1.2 ∼ 2.5 and α > 20 • or 1.5 6 P /d 6 4.0 and 10 • < α 6 20 • , where both cylinders generate vortices, with vortex shedding from the upstream cylinder at a much higher frequency than from the downstream, producing two streets of different widths and vortex strengths at x/d 6 5.0. The two streets interact vigorously, resulting in a single street of the lower-frequency vortices at x/d > 10. The vortices generated by the downstream cylinder are significantly stronger than those, originating from the upstream cylinder, in the other row. Mode T-I occurs at P /d > 2.5 and α = 20 • ∼ 88 • ; the two cylinders produce two streets of different vortex strengths and frequencies, both persisting beyond x/d = 10. At P /d > 2.5 and α > 88 • , the two cylinders generate two coupled streets, mostly anti-phased, of the same vortex strength and frequency (St ≈ 0.21), which is referred to as Mode T-II. The connection of the four modes with their distinct initial conditions, i.e. interactions between shear layers around the two cylinders, is discussed. † Author to whom correspondence should be addressed: mmyzhou@polyu.edu.hk 52 J. C. Hu and Y. Zhou IntroductionBecause of its fundamental importance and engineering significance, flow behind two circular cylinders has been investigated extensively. Most previous investigations focused on the wake of two side-by-side or inline cylinders because of their relative simplicity. As a result, our knowledge has been greatly improved on the two types of flow in terms of the dep...

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Section: Mode S-ibmentioning

confidence: 85%