Vortex Formation From a Forced System of Two Cylinders. Part I: Tandem Arrangement

Mahír, Necati; Rockwell, D.

doi:10.1006/jfls.1996.0032

Cited by 76 publications

(47 citation statements)

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“…As experimentally observed by Mahir et al [15] Von Kármán vortices form between cylinders when the gap is equal to 5D and Re = 160 whereas for Re = 200 no vortex forms between cylinders in configurations 2.5D and 1.5D. The Strouhal number obtained for configurations 1.5D is in agreement with the existing results, whereas slight differences are obtained in configurations corresponding to a gap of 2.5D and 5D with the experimental results of Mahir et al (2009)…”

Section: Configurationssupporting

confidence: 71%

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Fluid-structure interaction modeling with chimera grids in NSMB

et al. 2014

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Abstract. The paper presents the last few years of research at ICUBE, Team MECAFLU in the "Instabilité, Turbulence, Diphasique" group on the simulations of fluid-structure interactions applied to falling bodies using the NSMB solver. The first part of the study was devoted to the numerical study of a sphere falling in a vertical tube filled with a Poiseuille flow. Then the NSMB software has been extended to be able to take into account multiple moving bodies and the cases of two 2D cylinders falling in free air have been investigated. To prevent the collision of the two cylinders which is not consistent with the chimera method, an elastic shock has been implemented.Résumé. Ce papier présente les résultats de ces dernières années de recherche à ICUBE, dans l'équipe MECAFLU au sein du groupe "Instabilité, Turbulence, diphasique" sur les simulations des interactions fluide-structure appliquées à la chute des corps en utilisant le solveur NSMB. La première partie de l'étude a été consacrée à l'étude numérique d'une sphère en chute libre dans un tube vertical. Puis le solver NSMB a été étendu pour être en mesure de prendre en compte plusieurs corps en mouvement et les cas de deux cylindres 2D chute libre ont été étudiés. Pour éviter la collision des deux cylindres qui n'est pas possible avec la méthode chimère, un choc élastique a été mis en oeuvre.

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Section: Configurationssupporting

confidence: 71%

“…Re [24] and the experimental results obtained by Mahir et al [15].The results are summarized on Table 1.…”

Section: Configurationsmentioning

confidence: 85%

Fluid-structure interaction modeling with chimera grids in NSMB

et al. 2014

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“…Igarashi 1981Igarashi , 1984Kim & Durbin 1988;Xu & Zhou 2004) and forces on the cylinders (e.g. Zdravkovich 1977Zdravkovich , 1985Zdravkovich , 1987Mahir & Rockwell 1996). In practice, flow around two staggered cylinders is more important than that around side-by-side or inline arranged cylinders because of its more common occurrence in engineering.…”

Section: Introductionmentioning

confidence: 99%

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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“…More recently, Papaioannou et al 1 investigated the holes in the Arnold tongues of flow past two oscillating cylinders following the experimental evidence observed by Mahir and Rockwell. 17 The Arnold tongue indicates the lock-in regions in the amplitude versus frequency diagrams. It was first proven to exist in the experiment by Ongoren and Rockwell.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear spacing and frequency effects of an oscillating cylinder in the wake of a stationary cylinder

Yang

Zheng

2010

Physics of Fluids

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A numerical study of the laminar necklace vortex system and its effect on the wake for a circular cylinder Phys. Fluids 24, 073602 (2012) Nonlinear responses to a transversely oscillating cylinder in the wake of a stationary upstream cylinder are studied theoretically by using an immersed-boundary method at Re= 100. Response states are investigated in the three flow regimes for a tandem-cylinder system: the "vortex suppression" regime, the critical spacing regime, and the "vortex formation" regime. When the downstream cylinder is forced to oscillate at a fixed frequency and amplitude, the response state of flow around the two cylinders varies with different spacing between the two cylinders, while in the same flow regime, the response state can change with the oscillating frequency and amplitude of the downstream cylinder. Based on velocity phase portraits, each of the nonlinear response states can be categorized into one of the three states in the order of increasing chaotic levels: lock-in, transitional, or quasiperiodic. These states can also be correlated with velocity spectral behaviors. The discussions are conducted using near-wake velocity phase portraits, spectral analyses, and related vorticity fields. A general trend in the bifurcation diagrams of frequency spacing shows the smaller the spacing, frequency, or amplitude, the less chaotic the response state of the system and more likely the downstream and upstream wakes are in the same response state. The system is not locked-in in any case when the spacing between the cylinders is larger than the critical spacing. The near-wake velocity spectral behaviors correspond to the nonlinear response states, with narrow-banded peaks shown at the oscillation frequency and its harmonics in the lock-in cases. High frequency harmonic peaks, caused by interactions between the upstream wake and the downstream oscillating cylinder, are reduced in the near-wake velocity spectra of the upstream cylinder when the spacing increases.

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Vortex Formation From a Forced System of Two Cylinders. Part I: Tandem Arrangement

Cited by 76 publications

References 1 publication

Fluid-structure interaction modeling with chimera grids in NSMB

Fluid-structure interaction modeling with chimera grids in NSMB

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

Nonlinear spacing and frequency effects of an oscillating cylinder in the wake of a stationary cylinder

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