Wake transition in flow past a circular cylinder

Behara, Suresh; Mittal, Sanjay

doi:10.1063/1.3500692

Cited by 47 publications

(46 citation statements)

References 22 publications

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“…Roshko 1954;Taneda 1959;Norberg 1987;Monkewitz 1988;Williamson 1988;Eisenlohr & Eckelmann 1989;Strykowski & Sreenivasan 1990;Albarede & Monkewitz 1992;Dusek, Le Gal & Fraunie 1994;Zhang et al 1995;Barkley & Henderson 1996;Thompson, Hourigan & Sheridan 1996;Williamson 1996a,b;Henderson 1997;Thompson, Leweke & Williamson 2001;Kumar & Mittal 2006;Behara & Mittal 2010;Kumar & Mittal 2012, and many, many, others). This can be attributed to a number of factors including its symmetry, relevance to industry applications such as oil rig risers, chimneys, transmission wires, amongst other things and perhaps even the intrinsic aesthetic beauty of the laminar wake.…”

Section: Introductionmentioning

confidence: 95%

Low-Reynolds-number wakes of elliptical cylinders: from the circular cylinder to the normal flat plate

et al. 2014

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While the wake of a circular cylinder and, to a lesser extent, the normal flat plate have been studied in considerable detail, the wakes of elliptic cylinders have not received similar attention. However, the wakes from the first two bodies have considerably different characteristics, in terms of three-dimensional transition modes, and near-and far-wake structure. This paper focuses on elliptic cylinders, which span these two disparate cases. The Strouhal number and drag coefficient variations with Reynolds number are documented for the two-dimensional shedding regime. There are considerable differences from the standard circular cylinder curve. The different three-dimensional transition modes are also examined using Floquet stability analysis based on computed two-dimensional periodic base flows. As the cylinder aspect ratio (major to minor axis) is decreased, mode A is no longer unstable for aspect ratios below 0.25, as the wake deviates further from the standard Bénard-von Kármán state. For still smaller aspect ratios, another three-dimensional quasi-periodic mode becomes unstable, leading to a different transition scenario. Interestingly, for the 0.25 aspect ratio case, mode A restabilises above a Reynolds number of approximately 125, allowing the wake to return to a two-dimensional state, at least in the near wake. For the flat plate, three-dimensional simulations show that the shift in the Strouhal number from the two-dimensional value is gradual with Reynolds number, unlike the situation for the circular cylinder wake once mode A shedding develops. Dynamic mode decomposition is used to characterise the spatially evolving character of the wake as it undergoes transition from the primary Bénard-von Kármán-like near wake into a two-layered wake, through to a secondary Bénard-von Kármán-like wake further downstream, which in turn develops an even longer wavelength unsteadiness. It is also used to examine the differences in the two-and three-dimensional near-wake state, showing the increasing distortion of the two-dimensional rollers as the Reynolds number is increased.

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Section: Introductionmentioning

confidence: 95%

Low-Reynolds-number wakes of elliptical cylinders: from the circular cylinder to the normal flat plate

et al. 2014

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“…New phenomena are probably to be found in present DNS results in the transitional state. [60,61]. Therefore the present wake [1-3] satisfies the necessary conditions of DNS validity.…”

Section: Present Dns Characterizationmentioning

confidence: 79%

“…The above smoothness also arose in the isothermal wake shown earlier in Figure 6a. The 60 K. NOTO v mean is shown in Figure 7b, and is varied in the x direction. Variations in the z direction in v mean are relatively weak.…”

Section: 23mentioning

confidence: 99%

Direct Numerical Simulation of Air Heated Cylinder Wake in Transitional State. Part I: Cylinder Heating Effect on Strong Turbulence Anisotropy (STA), and Determination of STA Suppression

Noto

2014

Numerical Heat Transfer, Part B: Fundamentals

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A variation of strong turbulence anisotropy (STA) with cylinder heating, and, as a result, STA suppression, are here first elucidated in the air heated wake in the transitional state at Reynolds number Re ¼ 300 and Richardson number Ri ¼ 0.3. Simultaneously, new facts for variations of velocities u, v, and w, i.e., the upward, horizontal, and spanwise directions, and wake motion by cylinder heating are first elucidated. Here STA is defined such that, in velocities u, v, and w, laminar velocities arise in at least one directions but turbulence arises in the remainder of directions.1. STA is determined to arise in isothermal and heated wakes by employing the new method. With cylinder heating, STA is found to be suppressed because the turbulent region in w is decreased, the three-dimensionality is suppressed, but the twodimensionality and laminarization are enhanced in the heated wake. 2. With cylinder heating, the spanwise velocity jwj is found to be suppressed strongly in the probability density function (PDF), whose peak value is decreased strongly near w % 0, and becomes 20% of that in the isothermal wake. 3. The above decrease in jwj is found to be equivalent to the increase of laminar state in time records. With cylinder heating, the laminar region is increased, but the region with turbulence is decreased. 4. The wake stability is extremely different in thermal flows with or without turbulence in w. When w has turbulence, here u and v are laminar, STA arises, and the thermal flow field becomes the transitional state, has instability, and is destabilized. 5. When w does not have turbulence, and is laminar, velocities u, v, and w are all laminar, form only 3-D flow, and do not have turbulence anisotropy. The wake does not have instability, and is stabilized.

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“…The critical Reynolds number at which the mode becomes unstable varies between 150 and 190 (Williamson 1988;Karniadakis & Triantafyllou 1992;Zhang et al 1995;Williamson 1996a). This large range is probably due to oblique shedding in the experiments and due to the fact that the transition is slightly subcritical (Henderson 1997;Behara & Mittal 2010). However, Barkley (1996) showed by a Floquet analysis that the mode A becomes linearly unstable at a critical Reynolds number Re = 188.5 ± 1.0 at a spanwise wavelength equal to 3.96 ± 0.02 diameters.…”

Section: Introduction and Contextmentioning

confidence: 82%

Three-dimensional instabilities of a stratified cylinder wake

Bosco

Meunier²

2014

J. Fluid Mech.

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International audienceThis paper describes experimentally, numerically and theoretically how the three-dimensional instabilities of a cylinder wake are modified by the presence of a linear density stratification. The first part is focused on the case of a cylinder with a small tilt angle between the cylinder's axis and the vertical. The classical mode A well-known for a homogeneous fluid is still present. It is more unstable for moderate stratifications but it is stabilized by a strong stratification. The second part treats the case of a moderate tilt angle. For moderate stratifications, a new unstable mode appears, mode S, characterized by undulated layers of strong density gradients and axial flow. These structures correspond to Kelvin–Helmholtz billows created by the strong shear present in the critical layer of each tilted von Kármán vortex. The last two parts deal with the case of a strongly tilted cylinder. For a weak stratification, an instability (mode RT) appears far from the cylinder, due to the overturning of the isopycnals by the von Kármán vortices. For a strong stratification, a short wavelength unstable mode (mode L) appears, even in the absence of von Kármán vortices. It is probably due to the strong shear created by the lee waves upstream of a secondary recirculation bubble. A map of the four different unstable modes is established in terms of the three parameters of the study: the Reynolds number, the Froude number (characterizing the stratification) and the tilt angle

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Wake transition in flow past a circular cylinder

Cited by 47 publications

References 22 publications

Low-Reynolds-number wakes of elliptical cylinders: from the circular cylinder to the normal flat plate

Low-Reynolds-number wakes of elliptical cylinders: from the circular cylinder to the normal flat plate

Direct Numerical Simulation of Air Heated Cylinder Wake in Transitional State. Part I: Cylinder Heating Effect on Strong Turbulence Anisotropy (STA), and Determination of STA Suppression

Three-dimensional instabilities of a stratified cylinder wake

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