Flow regimes for a square cross-section cylinder in oscillatory flow

Tong, Feifei; Cheng, Liang; Xiong, Chengwang; Draper, Scott; An, Hongwei; Lou, Xiaofan

doi:10.1017/jfm.2016.829

Cited by 16 publications

(17 citation statements)

References 33 publications

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“…4) When an odd number is chosen as the denominator in the mode ratio, however, the wake flow generally leans to one side of the axis of oscillation and the mean transverse force is not zero. This feature resembles that of the asymmetric vortex formation around oscillatory bodies without the steady flow (Tatsuno & Bearman 1990;Tong et al 2017). The region of mode ratio with an odd denominator is generally narrow, and the flow is sensitive to a change of driving frequency.…”

Section: Discussionmentioning

confidence: 66%

“…The uneven distribution of vortices to the direction of oscillation is believed to be a manifestation of the asymmetric vortex formation induced by the cylinder oscillation, including the flow field of mode 1/2 as given in Figure 13 (b). In the case of oscillatory cylinders in still water, the shed vortices can move laterally to the axis of oscillation (Tatsuno & Bearman 1990;Tong et al 2015;Tong et al 2017).…”

Section: Wake Characteristics and Lift Coefficientmentioning

confidence: 99%

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Modes of synchronisation in the wake of a streamwise oscillatory cylinder

et al. 2017

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A numerical analysis of flow around a circular cylinder oscillating in-line with a steady flow is carried out over a range of driving frequencies $(f_{d})$ at relatively low amplitudes $(A)$ and a constant Reynolds number of 175 (based on the free-stream velocity). The vortex shedding is investigated, especially when the shedding frequency $(f_{s})$ synchronises with the driving frequency. A series of modes of synchronisation are presented, which are referred to as the $p/q$ modes, where $p$ and $q$ are natural numbers. When a $p/q$ mode occurs, $f_{s}$ is detuned to $(p/q)f_{d}$, representing the shedding of $p$ pairs of vortices over $q$ cycles of cylinder oscillation. The $p/q$ modes are further characterised by the periodicity of the transverse force over every $q$ cycles of oscillation and a spatial–temporal symmetry possessed by the global wake. The synchronisation modes $(p/q)$ with relatively small natural numbers are less sensitive to the change of external control parameters than those with large natural numbers, while the latter is featured with a narrow space of occurrence. Although the mode of synchronisation can be almost any rational ratio (as shown for $p$ and $q$ smaller than 10), the probability of occurrence of synchronisation modes with $q$ being an even number is much higher than $q$ being an odd number, which is believed to be influenced by the natural even distribution of vortices in the wake of a stationary cylinder.

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Section: Discussionmentioning

confidence: 66%

Section: Wake Characteristics and Lift Coefficientmentioning

confidence: 99%

Modes of synchronisation in the wake of a streamwise oscillatory cylinder

et al. 2017

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“…2006; Tong et al. 2017). The formation of the present regime D flow is believed to be a characteristic of flow around the cluster-scale structure, based on the detailed flow field to be presented below and the fact that regime D flow is also formed around solid circular and square cylinders (Tatsuno & Bearman 1990; Elston et al.…”

Section: Resultsmentioning

confidence: 99%

“…2006; Tong et al. 2017). The V-shape is formed by the shedding of different-sized vortices from either side of the cluster in each half-oscillation period.…”

Section: Resultsmentioning

confidence: 99%

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Oscillatory flow regimes around four cylinders in a diamond arrangement

et al. 2019

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Oscillatory flow around a cluster of four circular cylinders in a diamond arrangement is investigated using two-dimensional direct numerical simulation over Keulegan–Carpenter numbers (KC) ranging from 4 to 12 and Reynolds numbers (Re) from 40 to 230 at four gap-to-diameter ratios (G) of 0.5, 1, 2 and 4. Three types of flows, namely synchronous, quasi-periodic and desynchronized flows (along with 14 flow regimes) are mapped out in the (G, KC, Re)-parameter space. The observed flow characteristics around four cylinders in a diamond arrangement show a few unique features that are absent in the flow around four cylinders in a square arrangement reported by Tong et al. (J. Fluid Mech., vol. 769, 2015, pp. 298–336). These include (i) the dominance of flow around the cluster-scale structure at $G=0.5$ and 1, (ii) a substantial reduction of regime D flows in the regime maps, (iii) new quasi-periodic (phase trapping) $\text{D}^{\prime }$ (at $G=0.5$ and 1) and period-doubling $\text{A}^{\prime }$ flows (at $G=1$) and most noteworthily (iv) abnormal behaviours at ($G\leqslant 2$) (referred to as holes hereafter) such as the appearance of spatio-temporal synchronized flows in an area surrounded by a single type of synchronized flow in the regime map ($G=0.5$). The mode competition between the cluster-scale and cylinder-scale flows is identified as the key flow mechanism responsible for those unique flow features, with the support of evidence derived from quantitative analysis. Phase dynamics is introduced for the first time in bluff-body flows, to the best knowledge of the authors, to quantitatively interpret the flow response (e.g. quasi-periodic flow features) around the cluster. It is instrumental in revealing the nature of regime $\text{D}^{\prime }$ flows where the cluster-scale flow features are largely synchronized with the forcing of incoming oscillatory flow (phase trapping) but are modulated by localized flow features.

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Characteristics of the flow around a circular OWC-type wave energy converter supported by a bottom-sitting C-shaped structure

Huang

2020

Applied Ocean Research

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Flow regimes for a square cross-section cylinder in oscillatory flow

Cited by 16 publications

References 33 publications

Modes of synchronisation in the wake of a streamwise oscillatory cylinder

Modes of synchronisation in the wake of a streamwise oscillatory cylinder

Oscillatory flow regimes around four cylinders in a diamond arrangement

Characteristics of the flow around a circular OWC-type wave energy converter supported by a bottom-sitting C-shaped structure

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