Lift-up process in a heated-cylinder wake flow

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

doi:10.1063/1.2159031

Cited by 4 publications

(4 citation statements)

References 25 publications

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“…Similar flow structures have been found in numerically calculated results. 15 Counter-rotating vortices ͑indicated as CRV x ͒ are observed in the velocity field located around the stem, Fig. 8͑b͒.…”

Section: -4mentioning

confidence: 99%

“…These temperature gradients on their turn are linked to the counter-rotating vortices at the rear end of the cylinder. 15 The formation of the secondary vortical structures in the near-wake is discussed, 17 where a cyclic process is proposed. The present paper focuses on the development of the ⌳-shaped vortices toward the escaping mushroom-type structures.…”

Section: -4mentioning

confidence: 99%

“…However, for the mixed convection case, the threedimensional transition occurs at much lower Reynolds numbers ͑down to Re= 85 for Ri= 1.0 and water as the working fluid͒, which is referred to as the "mode-E" transition. 15 This three-dimensional transition is initialized in the near-wake by the formation of ⌳-shaped structures and manifests itself in the far-wake as escaping mushroom-type structures from the upper vortices. The legs of these ⌳-shaped vortices contain streamwise vorticity generated by baroclinic vorticity production due to the occurring spanwise temperature gradients.…”

Section: Introductionmentioning

confidence: 99%

“…These temperature gradients on their turn are linked to the counter-rotating vortices at the rear end of the cylinder. 15 The influence of these near-wake flow phenomena on the vortex shedding process is investigated in Ref. 16.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: -4mentioning

confidence: 99%

Section: -4mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Evolution of mushroom-type structures behind a heated cylinder

2007

Self Cite

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Cross-flow vortex-induced vibrations of a circular cylinder under stochastic inflow at low Reynolds number

Sourav,

Majumdar,

Sarkar

2024

Ocean Engineering

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Influence of thermal buoyancy on the wake dynamics of a heated square cylinder

Ali,

Hasan,

Sanghi

2024

J. Fluid Mech.

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Direct numerical simulation of the three-dimensional (3-D) wake transition of a heated square cylinder subjected to horizontal cross-flow is performed in the presence of buoyancy. In order to capture the effects of large-scale heating, a non-Oberbeck–Boussinesq model is utilized, which includes the governing equations for compressible gas flow. All computations are performed at low free stream Mach number $M=0.1$ using air (free stream Prandtl number, $Pr=0.71$ ) as the working fluid. The 3-D instability modes A and B, which correspond to free stream Reynolds numbers of 180 and 250, are observed with longer and shorter spanwise wavelengths, respectively, and the onset of three-dimensionality is triggered at a Reynolds number of 173. In the presence of buoyancy, baroclinic vorticity production in the near-wake plays an important role for streamwise vorticity generation. The chaotic wake of the Mode-A instability bifurcates into periodic and quasiperiodic wakes at various heating levels, expressed by the overheat ratio, $\varepsilon =(T_w-T_\infty )/T_\infty$ , where $T_w$ and $T_\infty$ are the temperature of the cylinder surface and the ambient air, respectively. At low heating ( $\varepsilon =0.2$ ), the 3-D Mode-A instability is suppressed leading to a two-dimensional wake flow. Further increase in heating, again brings back the three-dimensionality in the wake through Mode-E instability. The variation of thermophysical properties and the effective Reynolds number with increase in heating level around the cylinder is examined. It is shown that the effect of thermophysical properties competes with the baroclinic streamwise vorticity generation at higher levels of heating ( $\varepsilon \geqslant 0.4$ ) to control the 3-D modes and wake dynamics.

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Lift-up process in a heated-cylinder wake flow

Cited by 4 publications

References 25 publications

Evolution of mushroom-type structures behind a heated cylinder

Evolution of mushroom-type structures behind a heated cylinder

Cross-flow vortex-induced vibrations of a circular cylinder under stochastic inflow at low Reynolds number

Influence of thermal buoyancy on the wake dynamics of a heated square cylinder

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