Experimental and numerical investigation of the vortex formation process behind a heated cylinder

Ren, M Maosheng; Rindt, Ccm Camilo; Steenhoven, A.A. van

doi:10.1063/1.1765834

Cited by 24 publications

(16 citation statements)

References 18 publications

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“…Dumouchel et al [23] studied the transition from a two-dimensional (2-D) steady to a 2-D periodic wake at Re ¼ 52-61 of air. Kieft et al [24,25], Steenhoven and Rindt [26], and Ren et al [27] studied experimentally and numerically three-dimensional (3-D) vortex formation behind a heated cylinder at Re ¼ 75, 75, 100, and 100. Mass et al [28] visualized 3-D vortex formation behind a heated cylinder at Re ¼ 117 by an electrochemical tin precipitation method.…”

Section: Introductionmentioning

confidence: 99%

Numerical Computation of a New Vortex (A Cooled Vortex Street) and its Generation Mechanism in a Cooled Circular Cylinder Wake at Low Reynolds Number

Noto

Sugimura

2007

Numerical Heat Transfer, Part A: Applications

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A strongly cooled, circular cylinder wake with an upward main stream of air at low Reynolds number Re; i:e:, 15 5 Re 5 44, is analyzed numerically, and is elucidated as follows. (1) A new vortex street, i.e., a ''cooled vortex street,'' is discovered, develops in the range of computed Re; i:e:, 15 5 Re 5 44, has strong asymmetry, and is extremely different from the Karman vortex.(2) The vortex street occurring in the cooled wake is either the Karman vortex street or the cooled vortex street. No vortex street except these vortex streets ever occurs in a wake. (3) The critical Reynolds number Re c ; i:e:, the minimum Re occurring in the Karman vortex street by cooling a cylinder, is nearly 24. When the isothermal wake is cooled weakly, the Karman vortex street certainly develops at Re > 24, but never occurs at any cooling rate at Re < 24.The generation mechanism of the cooled vortex street is elucidated by employing the computed vorticity and temperature distributions as follows. (1) With an extreme increase in the cooling rate, the wake vorticity is generated strongly by the temperature gradient, the absolute value of vorticity in shear layers becomes extremely large, and the shear layers are elongated remarkably. The angle between shear layers and the wake width increase remarkably.(2) As a result, shear layers roll up considerably, and their tips reach the midplane alternately. Extremely large-scale vorticity-concentrated tips are generated, and move to the downstream. Thus a stable wake, i.e., the cooled vortex street, is generated. That is, the stable rolling of shear layers is realized only in the Karman and the cooled vortex streets.

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Section: Introductionmentioning

confidence: 99%

Numerical Computation of a New Vortex (A Cooled Vortex Street) and its Generation Mechanism in a Cooled Circular Cylinder Wake at Low Reynolds Number

Noto

Sugimura

2007

Numerical Heat Transfer, Part A: Applications

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“…Moreover, the experiments and calculations have been quantitatively compared in Ref. 16. There, a good agreement has been achieved between the experimentally measured and numerically calculated velocity fields in the ͑X-Y͒ plane at "in-plume" ͑spanwise position where the plume escapes downstream͒ and "out-of-plume" ͑spanwise position where no plume escapes downstream͒ positions, validating the numerical approach.…”

Section: D Spectral Element Methodsmentioning

confidence: 49%

“…15 The influence of these near-wake flow phenomena on the vortex shedding process is investigated in Ref. 16. It is shown that quite large differences occur between the different spanwise positions.…”

Section: Introductionmentioning

confidence: 99%

Evolution of mushroom-type structures behind a heated cylinder

2007

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The three-dimensional transition in the wake flow behind a heated cylinder occurs at a much lower Reynolds number than for the unheated case. The three-dimensional transition is initialized in the near-wake by the formation of Λ-shaped structures and manifests itself in the far-wake as escaping mushroom-type structures from the upper vortices. In this study, both experimental and numerical techniques are used to investigate the origin and development of these mushroom-type structures. The formation of the mushroom-type structures is associated with the occurrence of Λ-shaped vortices in the near-wake. Hot fluid between the legs and the head of the Λ-shaped structure is lifted up. This lift-up process together with the action of buoyancy pulls out hot fluid from the upper vortex cores, resulting in a mushroom-type structure, which is comprised of a so-called stem and cap. Hot fluid is continuously transported through the stem to the advancing front of the mushroom-type structure. Finally, a pinch-off phenomenon is observed of the cap, ending up as a buoyant vortex ring. An analytical model is presented for the pinch-off process.

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“…Escaping mushroom-type structures occur in the far wake with a spanwise distance of around twice the cylinder diameter. 12 Furthermore, it has also been shown in Ref.…”

Section: Introductionmentioning

confidence: 80%

“…12 Figure 6 shows a top view of the wake flow pattern, obtained by means of the tin-precipitation visualization technique. The flow is from bottom to top and the gravity direction is in the negative y direction.…”

Section: Coherent Structures In the Flow Fieldsmentioning

confidence: 99%

Lift-up process in a heated-cylinder wake flow

2006

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A three-dimensional flow transition behind a heated cylinder is analyzed at low Reynolds numbers: Re=O(100). Both visualizations and numerical simulations show that the transition manifests itself in the form of mushroom-type structures in the far wake and Λ-shaped structures in the near wake. The legs of the Λ-shaped structures coincide with streamwise vorticity regions. An intermediate stage is observed between the Λ-shaped structures and the escaping mushroom-type structures. This intermediate step is characterized by a lift-up process, which takes place in the center region between the legs and head of the Λ-shaped structures. As a result, hot fluid is being pulled out of the upper vortex core. Due to this lift-up process, mushroom-type structures are generated in the form of escaping vortex rings in the far wake.

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Experimental and numerical investigation of the vortex formation process behind a heated cylinder

Cited by 24 publications

References 18 publications

Numerical Computation of a New Vortex (A Cooled Vortex Street) and its Generation Mechanism in a Cooled Circular Cylinder Wake at Low Reynolds Number

Numerical Computation of a New Vortex (A Cooled Vortex Street) and its Generation Mechanism in a Cooled Circular Cylinder Wake at Low Reynolds Number

Evolution of mushroom-type structures behind a heated cylinder

Lift-up process in a heated-cylinder wake flow

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