Control of Vortex Shedding from a Square Cylinder

Chuanping, Shao; Wei, Qiang

doi:10.2514/1.28367

Cited by 17 publications

(6 citation statements)

References 17 publications

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“…Passive control methods, which do not need external power input, include control rod (Igarashi 1997; Zhang et al. 2005; Shao & Wei 2008), splitter plate (Bearman & Trueman 1972; Ali, Doolan & Wheatley 2011), corner modification (Hu, Zhou & Dalton 2006; Ueda et al. 2009; He, Li & Wang 2014), surface roughness (van Hinsberg, Schewe & Jacobs 2018), and so on.…”

Section: Introductionmentioning

confidence: 99%

“…According to whether there is external energy input, these methods can be classified into passive control methods and active control methods. Passive control methods, which do not need external power input, include control rod (Igarashi 1997;Zhang et al 2005;Shao & Wei 2008), splitter plate (Bearman & Trueman 1972;Ali, Doolan & Wheatley 2011), corner modification (Hu, Zhou & Dalton 2006;Ueda et al 2009;He, Li & Wang 2014), surface roughness (van Hinsberg, Schewe & Jacobs 2018), and so on. Active control methods, which need extra energy supply, include but are not limited to, rotation (Chatterjee & Gupta 2015a,b), oscillation (Bearman & Obasaju 1982;Fu et al 2017), plasma actuator (Anzai et al 2017), jet (Kim, Yang & Eom 2003;Akansu & Firat 2010a;Saha & Shrivastava 2015), synthetic jet (Akansu & Firat 2010b;Qu et al 2017) and blowing/suction (Sohankar, Khodadadi & Rangraz 2015;Sohankar & Najafi 2018).…”

Section: Introductionmentioning

confidence: 99%

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Effect of excitation frequency on flow characteristics around a square cylinder with a synthetic jet positioned at front surface

Wang

Feng

et al. 2019

J. Fluid Mech.

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The flow over a square cylinder controlled by a slot synthetic jet positioned at the front surface is investigated experimentally at different excitation frequencies. The Reynolds number based on the free-stream velocity and the side length of the square cylinder is 1000. The flow visualization was conducted using the laser-induced fluorescence technique. The velocity fields upstream and downstream of the square cylinder were measured synchronously with the two-dimensional time-resolved particle image velocimetry technique. Both the evolution of vortex structures and the characteristic frequencies of upstream and downstream flow fields are presented. The flow dynamics vary significantly with the excitation frequency at a fixed stroke length. During one excitation cycle, the synthetic jet vortex pair deflects to one side and later swings to the other side at a quite small excitation frequency of $f_{e}/f_{0}=0.6$, while it only deflects toward one side and does not turn to the other side at $f_{e}/f_{0}=1.0$. Compared with the natural case, the wake characteristics for the above two cases are not changed much by the synthetic jet adopted. At a moderate excitation frequency of $f_{e}/f_{0}=2.0$, the synthetic jet deflects upwards and downwards alternatively. The upstream flow field has a dominant frequency identical to half of the excitation frequency. Under the perturbations of the synthetic jet, two wake vortex pairs are formed per shedding cycle with a shedding frequency equal to that of the square cylinder without control. At a higher excitation frequency of $f_{e}/f_{0}=3.4$, the synthetic jet keeps deflecting to one side, and the upstream flow field is governed by the excitation frequency. The flow separation on the deflected side is suppressed effectively, and no periodic vortex shedding can be observed in the wake. Statistically, the velocity profiles also change with control. The recirculation bubble length in the wake is shortened, and the time-averaged velocity fluctuation is weakened remarkably. The control effects of the synthetic jet and the continuous jet are compared in this paper when placed at the front surface of a square cylinder.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of excitation frequency on flow characteristics around a square cylinder with a synthetic jet positioned at front surface

Wang

Feng

et al. 2019

J. Fluid Mech.

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“…These forces are generally undesired. To decrease them on the body, shear layers must be controlled before (boundary layer) and/or after (free shear layers) the separation [1][2][3][4][5][6][7][8][9][10]. The aim of this study is firstly to alter the near-wake structure of the cylinder using guiding plates, and then, to interpret the foregoing physics of the near-wake in terms of patterns of time-averaged vorticity and streamlines, timeaveraged and fluctuating velocity components, and spectral analysis; secondly to predict the trend of timeaveraged drag coefficient and root-mean-square of the fluctuating lift coefficient numerically in the absence of the direct force measurements.…”

Section: Introductionmentioning

confidence: 99%

An investigation of the near-wake flow structure of a cylinder with guiding plates

Ekinci¹,

Fırat²,

Ozkan³

et al. 2018

EPJ Web Conf.

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In this study, the flow behind a circular cylinder with a pair of outer identical guiding plates was investigated using particle image velocimetry (PIV) for various angular positions of the plates (i.e. α=±70°, ±100°, and ±130°). The gaps between these plates and cylinder are equal and are 0.3D. Experiments were carried out at a subcritical Reynolds (Re=ρ·U∞·D/μ) number of 7500, based on the cylinder diameter (D) and the flow velocity (U∞). The features of the near-wake with and without the guiding plates were interpreted in terms of patterns of time-averaged vorticity and streamlines, time-averaged and fluctuating velocity components. The spectral analysis was also carried out to determine the time-dependent variation of the transverse velocity at given locations in the near-wake. Two-dimensional computations of flow around circular cylinders with and without guiding plates have also been performed to predict the timeaveraged and root-mean-square of force coefficients of the various models. It was seen that the guiding plates at an appropriate angular position can lead to substantial attenuation, or retardation, of the process of large-scale vortex formation in the near-wake, thus can lead to vortex-induced vibration (VIV) suppression without any increase in drag.

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“…This passive system enabled 25% drag reduction over one decade of Reynolds numbers. Recently, Shao and Wei [5] investigated the modification of the flow around a square cylinder at high Reynolds number by means of a control rod. By displacing the control rod, the authors identified the location zones where the control was efficient.…”

Section: Introductionmentioning

confidence: 99%

“…Even though these examples, chosen among others, suggest that passive control can lead to significant improvements, the efficiency of this control strategy is often restricted to limited configurations. For instance, Shao and Wei [5] reported noticeable influences of the Reynolds number and the cross-section form of the control rod onto the control efficiency.…”

Section: Introductionmentioning

confidence: 99%

Biomimetic bluff body drag reduction by self-adaptive porous flaps

Mazellier

Feuvrier

Kourta

2011

Comptes Rendus. Mécanique

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The performances of an original passive control system based on a biomimetic approach are assessed by investigating the flow over a bluff-body. This control device consists in a couple of flaps made from the combination of a rigid plastic skeleton coated with a porous fabric mimicking the shaft and the vane of the bird's feathers, respectively. The sides of a square cylinder have been fitted with this system so as to enable the flaps to freely rotate around their leading edge. This feature allows the movable flaps to self-adapt to the flow conditions. Comparing both the uncontrolled and the controlled flow, a significant drag reduction (up to 22%) has been obtained over a broad range of Reynolds number. The investigation of the mean flow reveals a noticeable modification of the flow topology at large scale in the vicinity of the controlled cylinder accounting for the increase of the pressure base in comparison with the natural flow. Meanwhile, the study of the relative motion of both flaps points out that their dynamics is sensitive to the Reynolds number. Furthermore, the comparative study of the flow dynamics at large scale suggest a lock-in coupling of the flap motion and the vortex shedding.Comment: 19 pages, 17 figures, submitted to Comptes-Rendus de l' Acad\'emie des Sciences (M\'ecanique

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Control of Vortex Shedding from a Square Cylinder

Cited by 17 publications

References 17 publications

Effect of excitation frequency on flow characteristics around a square cylinder with a synthetic jet positioned at front surface

Effect of excitation frequency on flow characteristics around a square cylinder with a synthetic jet positioned at front surface

An investigation of the near-wake flow structure of a cylinder with guiding plates

Biomimetic bluff body drag reduction by self-adaptive porous flaps

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