Periodic Wakes of Low Aspect Ratio Cylinders With Free Hemispherical Ends

Schouveiler, Lionel; Provansal, Mireille

doi:10.1006/jfls.2000.0351

Cited by 18 publications

(13 citation statements)

References 25 publications

(30 reference statements)

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“…Meanwhile, highly three dimensional corner flow due to horseshoe tip vortex on the flat side of a cylinder was completely inhibited when the cylinder was mounted on a flat plate (Sumner et al, 2004). An increase in the critical Reynolds number due to the cylinder's low aspect ratio was also reported by Inoue and Sakuragi (2008), which concurred with previous works by others (Norberg, 1994;Schouveiler and Provansal, 2001).…”

Section: Introductionsupporting

confidence: 91%

“…The length of these bars represents the fluctuation of the rear stagnation point (measured from the 500 velocity field measurements). It should be noted that due to the pillar's low aspect ratio (L/D = 1.5) the critical Reynolds number is higher than for a 2-D cylinder, which is in good agreement with both numerical simulation (Fornberg, 1980;Green and Gerrard, 1993;Norberg, 1994) and experimental results at the macroscale Zovatto and Pedrizzetti, 2001;Schouveiler and Provansal, 2001).…”

Section: Flow Regime Behind a Circular Pillar In Microchannelsupporting

confidence: 83%

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The flow field around a micropillar confined in a microchannel

Jung

Kuo

Peles

et al. 2012

International Journal of Heat and Fluid Flow

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Section: Introductionsupporting

confidence: 91%

Section: Flow Regime Behind a Circular Pillar In Microchannelsupporting

confidence: 83%

The flow field around a micropillar confined in a microchannel

Jung

Kuo

Peles

et al. 2012

International Journal of Heat and Fluid Flow

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“…. ., Re 5 , including the present values, are summarised in Table 1 [81] 200 280 Provansal and Ormières [82] 180 280 310 360 Goldburg and Florsheim [83] 270 Sakamoto and Haniu [73] 280 300 420 Schouveiler and Provansal [84] 270 with Re is the increasing influence of the form drag with increasing Re due to the increasing pressure change around the body. As conclusion, the streamlining has a greater influence on the drag at low rather than at high Re and the size of the projected area has a greater influence at high rather than at low Re.…”

Section: Flow Around a Spherementioning

confidence: 96%

Lattice Boltzmann simulations to determine drag, lift and torque acting on non-spherical particles

2009

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“…However, for a cylinder held in an upcoming flow, the transition of its wake from a stationary to a periodic state is strongly dependent on the elongation ratio L/d of the cylinder. The experiments by Schouveiler & Provansal (2001) and Provansal, Schouveiler & Leweke (2004) for cylinders with free hemispherical ends and the numerical simulations by Inoue & Sakuragi (2008) for cylinders with free flat faces indicate that this transition occurs at increasing critical Reynolds numbers Re c when the elongation ratio decreases, typically Re c 100 for L/d = 5 and Re c 200 for L/d = 1. Furthermore, the numerical investigation by Inoue & Sakuragi (2008) disclose the existence of a variety of wake structures for 40 Re 300 and 1 < L/d < 100.…”

mentioning

confidence: 89%

Kinematics and wake of freely falling cylinders at moderate Reynolds numbers

2019

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We investigated experimentally the motion of elongated finite-length cylinders (length $L$, diameter $d$) freely falling under the effect of buoyancy in a low-viscosity fluid otherwise at rest. For cylinders with densities $\unicode[STIX]{x1D70C}_{c}$ close to the density $\unicode[STIX]{x1D70C}_{f}$ of the fluid ($\overline{\unicode[STIX]{x1D70C}}=\unicode[STIX]{x1D70C}_{c}/\unicode[STIX]{x1D70C}_{f}\simeq 1.16$), we explored the effect of the body volume by varying the Archimedes number $Ar$ (based on the body equivalent diameter) between 200 and 1100, as well as the effect of their length-to-diameter ratios $L/d$ ranging from 2 to 20. A shadowgraphy technique involving two cameras mounted on a travelling cart was used to track the cylinders along their fall over a distance longer than $30L$. A dedicated image processing algorithm was further implemented to properly reconstruct the position and orientation of the cylinders in the three-dimensional space. In the range of parameters explored, we identified three main types of paths, matching regimes known to exist for three-dimensional bodies (short-length cylinders, disks and spheres). Two of these are stationary, namely, the rectilinear motion and the large-amplitude oscillatory motion (also referred to as fluttering or zigzag motion), and their characterization is the focus of the present paper. Furthermore, in the transitional region between these two regimes, we observed irregular low-amplitude oscillatory motions, that may be assimilated to the A-regimes or quasi-vertical regimes of the literature. Flow visualization using dye released from the bodies uncovered the existence of different types of vortex shedding in the wake of the cylinders, according to the style of path. The detailed analysis of the body kinematics in the fluttering regime brought to light a series of remarkable properties. In particular, when normalized with the characteristic velocity scale $u_{0}=\sqrt{(\overline{\unicode[STIX]{x1D70C}}-1)gd}$ and the characteristic length scale $l_{0}=\sqrt{dL}$, the mean vertical velocity $\overline{u_{Z}}$ and the frequency $f$ of the oscillations become almost independent of $L/d$ and $Ar$. The use of the length scale $l_{0}$ and of the gravitational velocity scale to build the Strouhal number $St^{\ast }=fl_{0}/u_{0}$ allowed us to generalize to short ($0.1\leqslant L/d\leqslant 0.5$) and elongated cylinders ($2\leqslant L/d\leqslant 12$), the result $St^{\ast }\simeq 0.1$. An interpretation of $l_{0}$ as a characteristic length scale associated with the oscillatory recirculation thickness generated near the body ends is proposed. In addition, the rotation rate of the cylinders scales with $u_{0}/L$, for all $L/d$ and $Ar$ investigated. Furthermore, the phase difference between the oscillations of the velocity component $u$ along the cylinder axis and of the inclination angle $\unicode[STIX]{x1D703}$ of the cylinder is approximately constant, whatever the elongation ratio $L/d$ and the Archimedes number $Ar$.

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Periodic Wakes of Low Aspect Ratio Cylinders With Free Hemispherical Ends

Cited by 18 publications

References 25 publications

The flow field around a micropillar confined in a microchannel

The flow field around a micropillar confined in a microchannel

Lattice Boltzmann simulations to determine drag, lift and torque acting on non-spherical particles

Kinematics and wake of freely falling cylinders at moderate Reynolds numbers

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