Asymmetric cellular bi-stability in the gap between tandem cylinders

Aasland, Tale Egeberg; Pettersen, Bjørnar; Andersson, Helge I.; Jiang, Fengjian

doi:10.1017/jfm.2023.468

Cited by 6 publications

(17 citation statements)

References 38 publications

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“…This is consistent with the results of Aasland et al. (2023), who showed that there are two flow modes in the gap and near wake of straight tandem cylinders at and .…”

Section: Resultssupporting

confidence: 93%

“…In accordance with Aasland et al. (2023), the second mode may manifest locally, but in the present case the axial velocity enhances communication along the span, and this may trigger a switch of flow modes at additional spanwise locations. In the supplementary material and movie 2, the mode switch first occurs at , subsequently at and then finally at .…”

Section: Resultssupporting

confidence: 92%

“…This was confirmed by Aasland et al. (2023), who found that bi-stability manifests not only spanwise localised, but also asymmetrically in the gap; shedding may occur repeatedly from just one gap shear layer.…”

Section: Introductionsupporting

confidence: 56%

“…We believe that the short wavelength of the streamwise structures can be attributed to the large number of secondary vortices that arise from the interaction between the gap shear layers and near wake within the alternating reattachment/overshoot regime, previously described by Aasland et al. (2023) for the wake behind straight tandem cylinders.…”

Section: Resultsmentioning

confidence: 56%

“…For this combination of gap ratio and Reynolds number, alternating overshoot/reattachment is expected for straight tandem cylinders (Aasland et al. 2023), with the three-dimensional gap/wake instability mode T3 (Carmo, Meneghini & Sherwin 2010 a ).…”

Section: Flow Problem Formulation and Computational Aspectsmentioning

confidence: 99%

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Flow topology in the gap and wake of convex curved tandem cylinders

Aasland,

Pettersen,

Andersson

et al. 2023

J. Fluid Mech.

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Flow around curved tandem cylinders in the convex configuration has been studied by means of direct numerical simulations, for a Reynolds number of 500 and a nominal gap ratio of 3.0. Spanwise variation of flow regimes, as well as curvature-induced axial velocity, leads to an exceedingly complex vortex dynamics in the wake. Both parallel and oblique vortex shedding are observed. Oblique shedding is connected to repeated occurrences of dislocations. The dislocations are caused by two main mechanisms: frequency differences in the upper part of the curved geometry and shedding of gap vortices into the lower near wake. Both types of dislocations are closely associated with a mode switch in the gap. In parts of the gap, there is low-frequency quasi-periodic asymmetry of the gap vortices, where the flow is biased to one side of the gap for intervals of several wake vortex shedding periods. The switch from side to side is associated with a surge of the vertical velocity, and the frequency of the switch is similar to that of long-term variation of the recirculation length in the lower gap.

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“…This is consistent with the results of Aasland et al. (2023), who showed that there are two flow modes in the gap and near wake of straight tandem cylinders at and .…”

Section: Resultssupporting

confidence: 93%

Section: Resultssupporting

confidence: 92%

Section: Introductionsupporting

confidence: 56%

Section: Resultsmentioning

confidence: 56%

Section: Flow Problem Formulation and Computational Aspectsmentioning

confidence: 99%

See 3 more Smart Citations

Flow topology in the gap and wake of convex curved tandem cylinders

Aasland,

Pettersen,

Andersson

et al. 2023

J. Fluid Mech.

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Wake of two tandem square cylinders

Zhou,

Hao,

Alam

2024

J. Fluid Mech.

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The wake of two tandem square cylinders of identical width (d) is experimentally studied, with a view to understanding the dependence of the flow structure, aerodynamics forces and Strouhal number on the centre-to-centre spacing ratio L/d and Reynolds number Re, where L is the distance between the cylinder centres. Extensive measurements are carried out, using hot-wire, particle imaging velocimetry, laser-induced fluorescence flow visualization, surface-oil-flow visualization and surface pressure scanning techniques, for L/d = 1.0 ~ 5.0 and Re ≡ U∞d/ν = 2.8 × (103 ~ 104), where U∞ is the free-stream velocity and ν is the kinematic viscosity of the fluid. The flow is classified into four regimes, i.e. the extended-body (L/d ≤ 1.5–2.0), reattachment (1.5–2.0 < L/d < 2.7–3.2), co-shedding (L/d ≥ 3.0–3.4) and transition (2.7 ≤ L/d ≤ 3.3) where both reattachment and co-shedding phenomena may take place. The mean drag and fluctuating drag and lift exhibit distinct features for different flow regimes, which is fully consistent with the proposed flow classification. Comparison is made between this flow and the wake of two tandem circular cylinders, which provides valuable insight into the profound effect of the flow separation point and the presence of sharp corners on the flow development and classification.

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Coexistence of natural and forced vortex dislocations in step cylinder flow

Tian,

Zhu,

Holmedal

2023

Physics of Fluids

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The wake behind a step cylinder [consisting of a small diameter cylinder (d) and a large diameter cylinder (D)] with diameter ratio D/d=2 at Reynolds number ReD = 200 (the mode A* regime) is simulated by direct numerical simulations. New detailed information of the interaction between natural vortex dislocations and forced vortex dislocations is described. In the large cylinder wake, the forced and natural vortex dislocations coexist. The regular formation of forced vortex dislocation is found to be delayed under the effect of natural vortex dislocations. The occurrence of natural vortex dislocations is suppressed in the large cylinder wake close to the small cylinder. Moreover, the effect of vortex dislocations on structural loads is described. The results of this paper provide a more thorough understanding of the formation and interaction between the natural and forced vortex dislocations.

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Asymmetric cellular bi-stability in the gap between tandem cylinders

Cited by 6 publications

References 38 publications

Flow topology in the gap and wake of convex curved tandem cylinders

Flow topology in the gap and wake of convex curved tandem cylinders

Wake of two tandem square cylinders

Coexistence of natural and forced vortex dislocations in step cylinder flow

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