The flow past large numbers of cylinders in tandem

Hosseini, Negar; Griffith, Martin D.; Leontini, Justin

doi:10.1016/j.jfluidstructs.2020.103103

Cited by 28 publications

(5 citation statements)

References 62 publications

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“…This Kármán-like vortex has also been observed in the study of cylinders in tandem (Hosseini et al. 2020). Moreover, this in-patch Kármán-like structure may explain why natural patches may not keep elongating downstream unrestrictedly but present an equilibrium length.…”

Section: Discussionsupporting

confidence: 67%

“…This interaction leads to the formation of an in-patch Kármán-like vortex, which results in vortex intensity dissipation and velocity recovery as indicated in figures 5 and 6. This Kármán-like vortex has also been observed in the study of cylinders in tandem (Hosseini et al 2020). Moreover, this in-patch Kármán-like structure may explain why natural patches may not keep elongating downstream unrestrictedly but present an equilibrium length.…”

Section: Coexistence Between Kh Vortex Street and Wake Vortex Streetsupporting

confidence: 60%

“…Meanwhile, the delay effect of the bleed flow will be weakened due to its reduced velocity, thus, the steady wake length is expected to be shortened as patch length increases. A numerical investigation of flow in a multi-cylinder tandem array has demonstrated that extending the length of a porous obstruction promoted the formation of a von Kármán vortex street (Hosseini, Griffith & Leontini 2020). Moreover, how the along-edge vortex structure interacts or impacts the wake vortex structure (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study on the combined effects of patch density and elongation on wake structure behind a rectangular porous patch

et al. 2023

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This paper presents an experimental study on how both variable solid volume fractions and aspect ratios (length/width) of a centre-channel rectangular porous patch under aligned configuration of rigid and emergent stems impact the flow behaviour and wake structure. This study forms an essential extension to the existing fundamentals and knowledge on this topic. Through rigorous experimental tests by velocity measurement and dye visualization, the aspect ratio, rarely addressed before, is confirmed to play a critical role. Vortex street, unable to be triggered under a low solid volume fraction, however, can be generated by elongating the patch (increasing the aspect ratio). The key reason is that patch elongation promotes the generation of the wake vortex street by producing a relatively high transverse velocity gradient in the wake region. Meanwhile, Kelvin–Helmholtz vortex streets are triggered along the two patch lateral edges, re-increasing the in-patch velocity and imposing contributions to the wake vortex streets generation. By scaling the characteristic velocity (at the wake vortex initiation position and patch trailing edge) and solid volume fraction with the patch aspect ratio, three non-dimensional threshold maps can be established to express the combined effects of the solid volume fraction and aspect ratio on the initiation of the wake vortex street. They could be alternatively used for theoretical analysis and implementation on wake formation and structure subject to parameter availability.

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Section: Discussionsupporting

confidence: 67%

Section: Coexistence Between Kh Vortex Street and Wake Vortex Streetsupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

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Experimental study on the combined effects of patch density and elongation on wake structure behind a rectangular porous patch

et al. 2023

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“…This is high enough to allow complex dynamics, but not so high to completely invalidate the two-dimensional assumption [3]. Our previous studies have also shown the dynamics to be reasonably insensitive to Re [6].…”

Section: Problem Setupmentioning

confidence: 86%

Flow-induced vibrations in cylinder arrays are moderated by convective instabilities

Hosseini¹,

Griffith²,

Leontini³

2020

Australasian Fluid Mechanics Conference (AFMC)

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This study investigates the flow in rows of large numbers of cylinders. When the cylinders are fixed in place, we show that the dynamics are dictated by a cascade of regimes -fluctuation, vortex shedding, convectively unstable region -that repeat as the flow traverses the row, the convectively unstable regions acting as "event horizons" allowing no information to pass upstream. For moderate cylinder spacings, we show that these same regimes govern the flow-induced vibration response when the cylinders are elastically-mounted.

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“…It was demonstrated that the Reynolds number, power-law index, and gap ratio significantly affect the streamline as well as the surface pressure and lift coefficients of both the cylinders. Although most of the studies devoted to a pair of cylinders in tandem, Hosseini et al, (2020) reported flow in a multi-cylinder tandem array to reveal the effects of increasing the number of cylinders on the flow field for low Reynolds numbers (Re<200). Basically, three flow types were identified based on the behavior of the flow in the gap between the cylinders.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of flow over tandem and side-by-side cylinders

Bayraktar¹

2021

Seatific

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In the present paper, two-dimensional unsteady flows over circular cross-section cylinders are analyzed numerically. The effects of placement of the cylinders are investigated for two different arrangements: tandem and side-by-side. Several turbulence models are tested, and it is found that Spalart-Allmaras turbulence model is the best among one-and two-equation turbulence models. The most appropriate time step, which is one of the important parameters in unsteady simulations, is found as 0.002 seconds. After successful validations, the cylinders are positioned as side-by-side and tandem. The effects of the arrangement on flow regime, drag coefficient, lift coefficient and Strouhal number are presented for various distances between the cylinders. It is found that the flow is almost steady without any vortex in the gap when cylinders are in tandem and the gap between them is low. In contrast, the interactions are strong in case of side-by-side arrangement at the lowest gap. When the gap increases, the flow is affected that results in change on the global parameters.

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The flow past large numbers of cylinders in tandem

Cited by 28 publications

References 62 publications

Experimental study on the combined effects of patch density and elongation on wake structure behind a rectangular porous patch

Experimental study on the combined effects of patch density and elongation on wake structure behind a rectangular porous patch

Flow-induced vibrations in cylinder arrays are moderated by convective instabilities

Numerical investigation of flow over tandem and side-by-side cylinders

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