Characterization of three-dimensional vortical structures in the wake past a circular cylinder in the transitional regime

Sarwar, Wasim; Mellibovsky, Fernando

doi:10.1063/5.0011311

Cited by 32 publications

(5 citation statements)

References 64 publications

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“…After some initial transients, the perturbation field will naturally align with the fastest growing mode (or the slowest decaying) and thus provide information on the stability of the underlying two-dimensional flow. The analysis is analogous to that followed by Sarwar and Mellibovsky [29] in analysing the spanwise stability of two-dimensional chaotic…”

Section: Stability Of Two-dimensional Solutions To Spanwise-dependent...mentioning

confidence: 92%

Onset of temporal dynamics within a low reynolds-number laminar fluidic oscillator

Sarwar

Bergadà

Mellibovsky

2021

Applied Mathematical Modelling

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Section: Stability Of Two-dimensional Solutions To Spanwise-dependent...mentioning

confidence: 92%

Onset of temporal dynamics within a low reynolds-number laminar fluidic oscillator

Sarwar

Bergadà

Mellibovsky

2021

Applied Mathematical Modelling

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“…The localised spanwise length scale is estimated as where is the spanwise phase of calculated from the Hilbert transform as where is the local amplitude. Following the work by Sarwar & Mellibovsky (2020), (5.4) and (5.5) are calculated by adopting the approximation of . The probability density function (PDF) of along the direction, namely , is then used to characterise the distributions of .…”

Section: Three-dimensional Wake Transitionsmentioning

confidence: 99%

“…The probability density function (PDF) of along the direction, namely , is then used to characterise the distributions of . This method is superior for characterising the length scale of the flow with localised flow features and has also been used in the studies of wake flows behind a bluff body (Sarwar & Mellibovsky 2020; Ong & Yin 2022).…”

Section: Three-dimensional Wake Transitionsmentioning

confidence: 99%

Three-dimensional wake transitions of steady flow past two side-by-side cylinders

Ren,

Liu,

Cheng

et al. 2023

J. Fluid Mech.

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Three-dimensional (3-D) wake transitions of a steady flow past two side-by-side circular cylinders are investigated through Floquet analysis and direct numerical simulations (DNS) over the gap-to-diameter ratio $g^*$ up to 3.5 and Reynolds number ${\textit {Re}}$ up to 400. When the flows behind two cylinders form in-phase and anti-phase wakes at large $g^*$ , the wake transition is similar to the isolated cylinder counterpart, with the critical ${\textit {Re}}$ for the onset of 3-D transition ( ${\textit {Re}}_{cr-1}$ ) happens at around 180. At small $g^*$ , 3-D transition becomes interestingly complex due to the distinct characteristics formed in base flows. The ${\textit {Re}}_{cr-1}$ suddenly drops to around 60–100 and forms distinct variation trends with $g^*$ . Precisely, the ${\textit {Re}}_{cr-1}$ of the single symmetric wake (SS, $g^*\lessapprox 0.25$ ) is more than half of the isolated cylinder counterpart due to the large length scale of the SS wake. Only mode A is detected in SS. In the asymmetric single wake (ASS, $g^* \approx 0.25\unicode{x2013}0.6$ ) and flip-flop wake (FF, $g^* \approx 0.6\unicode{x2013}1.8$ ), the 3-D transition develops at ${\textit {Re}} \approx 103\unicode{x2013}60$ and 75–60, respectively. The decrease in ${\textit {Re}}_{cr-1}$ with increasing $g^*$ is because of the increased level of wake asymmetry in ASS and irregular vortex shedding in FF. Floquet analysis predicts two new unstable modes, namely mode A $'$ and subharmonic mode C $'$ , of ASS. Both modes are transient features in 3-D DNS and the flow eventually saturates into a new 3-D mode, mode ASS. The gap flow of mode ASS is distinctly characterised by its time-independent spanwise waviness structure that is deflected towards different transverse directions with a long wavelength of about $14$ cylinder diameters. The 3-D mode of the FF is irregular both temporally and spatially. Variations of ${\textit {Re}}_{cr-1}$ with $g^*$ , the characteristics and the physical mechanisms of each 3-D mode are discussed in this study.

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“…The saturation to turbulent state has been reported to occur at Re 500 [7] through a physical mechanism of period-doubling cascade, which has been dubbed a 'fast' transition. Following the 'fast' transition, the spanwise length scale of three-dimensionality at a moderately high Re regime was characterized by many researchers [16,17].…”

Section: Introductionmentioning

confidence: 99%

“…In the current work, we study a circular cylinder in cross flow at Re = 2000 actuated via space-independent, time-dependent forcing at twice the natural vortex shedding frequency. The study is 2D, despite the actual flow being 3D at the coincident Re [17]; however, we are mainly interested in the qualitative features of the interaction of time-periodic fluidic active flow control with a chaotic cylinder wake. We are primarily interested in the influence of forcing amplitude on the wake dynamics.…”

Section: Introductionmentioning

confidence: 99%

Transition to Periodic Behaviour of Flow Past a Circular Cylinder under the Action of Fluidic Actuation in the Transitional Regime

et al. 2021

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This study focuses on the numerical investigation of the underlying mechanism of transition from chaotic to periodic dynamics of circular cylinder wake under the action of time-dependent fluidic actuation at the Reynolds number = 2000. The forcing is realized by blowing and suction from the slits located at ±90∘ on the top and bottom surfaces of the cylinder. The inverse period-doubling cascade is the underlying physical mechanism underpinning the wake transition from mild chaos to perfectly periodic dynamics in the spanwise-independent, time-dependent forcing at twice the natural vortex-shedding frequency.

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Characterization of three-dimensional vortical structures in the wake past a circular cylinder in the transitional regime

Cited by 32 publications

References 64 publications

Onset of temporal dynamics within a low reynolds-number laminar fluidic oscillator

Onset of temporal dynamics within a low reynolds-number laminar fluidic oscillator

Three-dimensional wake transitions of steady flow past two side-by-side cylinders

Transition to Periodic Behaviour of Flow Past a Circular Cylinder under the Action of Fluidic Actuation in the Transitional Regime

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