Flows past rotating cylinders next to a wall

Rao, Anil; Stewart, Bronwyn; Thompson, Mark C.; Leweke, Thomas; Hourigan, Kerry

doi:10.1016/j.jfluidstructs.2011.03.019

Cited by 50 publications

(57 citation statements)

References 31 publications

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“…It has been shown previously that the flow structures visualised in the experiments and those observed numerically are in good agreement with G/d = 0.005 (Stewart et al 2010(Stewart et al , 2006Rao et al 2011), while reducing the gap ratio has little effect on flow quantities of interest (Stewart et al 2010) Thus a gap ratio G/d of 0.005 was used throughout this investigation.…”

Section: Domain Size and Resolution Studiessupporting

confidence: 63%

“…Prograde rolling (α > 0) was found to destabilise the flow whereas retrograde rotation (α < 0) delayed the onset of unsteady flow. This was later confirmed/extended in a study by Rao et al (2011) for which higher values of α were considered.…”

Section: Introductionsupporting

confidence: 57%

“…Whilst higher-order timestepping methods could be employed, because typically several hundred time-steps are required per shedding cycle to guarantee stability of the iterative approach, there is no discernible improvement in accuracy of the overall solution. The solver is explained in more detail by Thompson et al (2006), and has widely been tested, validated and used for studies of flows around bluff bodies such as cylinders (Thompson et al 2001b;Ryan et al 2005;Rao et al 2011) and spheres (Thompson et al 2001a;Rao et al 2012;Thompson et al 2006). This code has also been modified to determine the linear stability of base flows, as explained in section 2.4 below.…”

Section: Numerical Schemementioning

confidence: 99%

“…At Re = 170, Taneda (1965) observed a single row of vortices for a cylinder moving near a wall. In the unsteady regime, vortex pairs with a net rotation appear in the wake as a result of the interaction between the shear layer shed from the top of the cylinder and induced secondary shedding from the wall boundary layer vorticity downstream (Stewart et al 2010;Rao et al 2011). Unlike the case of a cylinder placed in a free stream but similar to the flow over a backward facing step, the wake undergoes a transition to threedimensionality before the onset to two-dimensional vortex shedding (Stewart et al 2010;Rao et al 2011).…”

Section: Introductionmentioning

confidence: 99%

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Two- and three-dimensional wake transitions of an impulsively started uniformly rolling circular cylinder

et al. 2017

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This paper presents the characteristics of the different stages in the evolution of the wake of a circular cylinder rolling without slipping along a wall at constant speed, acquired through numerical stability analysis and two-and three-dimensional numerical simulations. Reynolds numbers between 30 and 300 are considered. Of importance in this study is the transition to three-dimensionality from the underlying two-dimensional periodic flow and, in particular, the way that the associated transitions influence the fluid forces exerted on the cylinder, and the development and the structure of the wake. It is found that the steady two-dimensional flow becomes unstable to threedimensional perturbations at Re c,3D = 37, and that the transition to unsteady twodimensional flow -or periodic vortex shedding -occurs at Re c,2D = 88, thus validating and refining the results of Stewart et al. (2010). The main focus here is for Reynolds numbers beyond the transition to unsteady flow at Re c,2D = 88. From impulsive start up, the wake almost immediately undergoes transition to a periodic two-dimensional wake state, which, in turn, is three-dimensionally unstable. Thus, the previous threedimensional stability analysis based on the two-dimensional steady flow provides only an element of the full story. Floquet analysis based on the periodic two-dimensional flow was undertaken and new three-dimensional instability modes were revealed. The results suggest that an impulsively started cylinder rolling along a surface at constant velocity for Re 90 will result in the rapid development of a periodic two-dimensional wake that will be maintained for a considerable time prior to the wake undergoing threedimensional transition. Of interest, the mean lift and drag coefficients obtained from full three-dimensional simulations match predictions from two-dimensional simulations to within a few percent.

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Section: Domain Size and Resolution Studiessupporting

confidence: 63%

Section: Introductionsupporting

confidence: 57%

Section: Numerical Schemementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Two- and three-dimensional wake transitions of an impulsively started uniformly rolling circular cylinder

et al. 2017

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“…In the flow past a rotating cylinder near a plane wall, the gap width is an important parameter in determining the forces on the cylinder, vortex shedding (Cheng & Luo 2007) and three-dimensional instability (Rao et al (2011) and Rao et al (2015)). In the application of rotating control cylinders to bluff body flow control, Mittal (2001) found that the gap between the main and control cylinders is a critical parameter and sensitivity to the gap changes with Reynolds number.…”

Section: Introductionmentioning

confidence: 99%

Flow control with rotating cylinders

et al. 2017

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We study the use of small counter-rotating cylinders to control the streaming flow past a larger main cylinder for drag reduction. In a water tunnel experiment at a Reynolds number of 47, 000 with a three-dimensional and turbulent wake, Particle Image Velocimetry (PIV) measurements show that rotating cylinders narrow the mean wake and shorten the recirculation length. The drag of the main cylinder was measured to reduce by up to 45%. To examine the physical mechanism of the flow control in detail, a series of two-dimensional numerical simulations at a Reynolds number equal to 500 were conducted. These simulations investigated a range of control cylinder diameters in addition to rotation rates and gaps to the main cylinder. Effectively controlled simulated flows present a streamline that separates from the main cylinder, passes around the control cylinder, and reattaches to the main cylinder at a higher pressure. The computed pressure recovery from the separation to reattachment points collapse with respect to a new scaling, which indicates that the control mechanism is viscous.

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Analysis of the convective heat transfer and flow behavior around two counter‐rotating side‐by‐side cylinders

Darvishyadegari

Hassanzadeh

2018

Heat Trans. Asian Res.

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This study presents details of the heat and fluid flow around two counter-rotating cylinders. For this goal, three different nondimensional gap spaces such as G/D = 1.5, 2.0, and 3.0 are examined in the constant Reynolds number of 200 and Prandtl number of 7.0. In addition, computations are carried out at various nondimensional rotating speeds (R.S) in the range from 0 to 4. The obtained results are validated against the available data in the open literature for stationary cases.The results showed that the flow structure, vortex shedding process, and exerted forces on the cylinders strongly depended on the R.S and G/D. Reductions of the drag coefficients are observed for both cylinders with increasing the R.S due to suppression of the wake downstream of the cylinders at low R.S and eliminating the vortex shedding process at high R.S. Finally, it is demonstrated that, regardless of the G/D value, increasing the R.S

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Flows past rotating cylinders next to a wall

Cited by 50 publications

References 31 publications

Two- and three-dimensional wake transitions of an impulsively started uniformly rolling circular cylinder

Two- and three-dimensional wake transitions of an impulsively started uniformly rolling circular cylinder

Flow control with rotating cylinders

Analysis of the convective heat transfer and flow behavior around two counter‐rotating side‐by‐side cylinders

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