Turbulence properties of an axisymmetric separation-and-reattaching flow

Kiya, Masaru; Mochizuki, Osamu; Tamura, Hisataka; Nozawa, Toru; Ishikawa, Ryo; Kushioka, Kiyonori

doi:10.2514/3.10682

Cited by 21 publications

(11 citation statements)

References 16 publications

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“…For example, wake control was performed by Higuchi et al (2004) who conducted an active openloop control of a disk wake, the limiting case of small L/D with fully separated shear layer, and modified the size of the recirculation zone in the wake with increased mean drag. Kiya et al (1991) found two peaks in the surface pressure spectra, one associated with the shear layer flapping and another associated with the vortex shedding in the separating region. The present structure appears to be smaller in scale, but awaits for time-resolved PIV data being collected.…”

Section: Flow Visualization and Unsteady Velocity Fieldmentioning

confidence: 95%

“…In one flowfield study, Ota (1975) used a combination of flow direction probe, hot wire and Pitot tube to measure the mean flowfield within the separation bubble and in the boundary layer on a cylinder of fineness ratio 10. Kiya et al (1991) used the split film, hot wire and pressure transducer to probe the separation and reattaching flow. They found a cellular structure in the reattachment region.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Axial flow over a blunt circular cylinder with and without shear layer reattachment

Handa

Langen

Sawada

et al. 2006

Journal of Fluids and Structures

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Section: Flow Visualization and Unsteady Velocity Fieldmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Axial flow over a blunt circular cylinder with and without shear layer reattachment

Handa

Langen

Sawada

et al. 2006

Journal of Fluids and Structures

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“…8 and 9, indicating reasonably good agreement at the similar accuracy to that by Rastgou and Saedodin. 35 Furthermore, the comparisons between the experimental results of Ota 36 (Re ¼ 56 200) and Kiya et al 37 (Re ¼ 10 5 ) also con¯rm that small discrepancy may exist in the reverse°ow region depending on the Reynolds number. One of the key characteristics in Rastgou and Saedodin's study is that the reattachment length that is de¯ned as the distance between the separation point and the reattachment point.…”

Section: Axisymmetric Separated and Reattached°owmentioning

confidence: 82%

Lattice Boltzmann method for axisymmetric turbulent flows

Wang

Zhou

2015

Int. J. Mod. Phys. C

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A lattice Boltzmann model for axisymmetric turbulent°ows is developed. It is a further development of the enhanced axisymmetric lattice Boltzmann method (AxLABr). The turbulent°o w is e±ciently and naturally simulated through incorporation of the standard subgrid-scale (SGS) stress model into the axisymmetric lattice Boltzmann equation in a consistent manner with the lattice gas dynamics. The model is veri¯ed by applying it to three typical cases in engineering: (i) pipe°ow through an abrupt axisymmetric constriction, (ii) axisymmetric separated and reattached°ow and (iii) pulsatile°ows in a stenotic vessel. The numerical results obtained using the present method are compared with experimental data and other available numerical solutions, indicating good agreements. The model is simple and is able to predict axisymmetric turbulent°ows at good accuracy.

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“…To explain this, we are needed to investigate such complicated three-dimensional flow without clear periodicities, more precisely. (29) Re = 7.5×10 3 −1.5×10 5 Berger et al (1990) (29) 2D prism (d/t = ∞), Re = 5.0×10 3 Okajima et al (1984) (26) ,(1990) (27) (25) In comparison with the rod, whose St is much complicated than those of the pipe and the two-dimensional prism even for l/t < 4, in contrast to C pb , we could suppose that the predominant periodically-fluctuating phenomena of the pipe and the two-dimensional prism are related with the 'shear layer flapping motion (30) ' with St = 0.20 for l/t = ∞ or the base-pressure fluctuation (24) with St = 0.17 for l/t = 2.54 -3.58, from a qualitative point of view. To consider the relation between the St for low d/t like the rod and the alternating regular ring-vortex shedding seems less-founded.…”

Section: Periodicity and Strouhal Numbermentioning

confidence: 99%

High-Reynolds-Number Flow past a Pipe

Hirata

Sakata

Yajima

et al. 2013

JFST

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The present aim is to reveal the flow past a pipe which is immersed parallel to the mainstream at high Reynolds numbers. In a wind tunnel, we carry out (1) base-pressure measurements, (2) velocity-fluctuation measurements using a hot-wire anemometer and (3) flow visualisations by a smoke-wire method with PIV analyses, where we take consecutive picutures using a high-speed camcorder to obtain quantitative flow-field information such as velocity vector and vorticity. The tested parameter ranges are as follows: Re = 2.0×10 3 -1.3×10 4, d/t = 4.0 -10.0 and l/t = 1.0 -10.0, where Re, d, t and l are the Reynolds number, mean diameter, thickness and length of the pipe, respectively. As a result, the Re effects are negligible. The base-suction coefficient C pb monotonically decreases with decreasing d/t, or with increasing l/t. We propose a unified formula to predict C pb , which are consistent with both a two-dimensional prism and a rod for l/t < 4.0 in addition to a ring. In contrast, the Strouhal number St almost coincides with that for a two-dimensional prism at any l/t, if we can detected any dominant frequencies. In addition, we conduct flow visualisations, and reveal the effects upon axisymmetry of wake. Finally, we classify the flow into three modes based on both periodicity and axisymmetry. Such a modal classification reveals that the enhancement of flow's irregularity corresponds to the decrease of C pb .Key Words: IntroductionWhile the flow past a bluff body at higher Reynolds numbers often becomes important in many practical aspects, it is one of rather later topics in the long history of fluid mechanics. Among such bluff-body-flow problems, there have been less researches concerning three-dimensional bluff bodies, in comparison with well-researched two-dimensional ones such as a circular cylinder which has advantages in some compatibilities with analytical, experimental and numerical approaches.As basic three-dimensional bluff bodies, it seems natural to consider axisymmetrical bodies with simple geometries like a sphere and a disc, whose knowledge is useful in the analyses of flying or suspended objects. But, even the flow past such a simple axisymmetrical body has not been revealed enough, despite of the wide ranges of its engineering applicabilities, in comparison with a circular cylinder.The present study concerns the flow past another simple axisymmetrical bluff body, a pipe or a tube, which is immersed parallel to the mainstream at high Reynolds numbers. The researches on the flow have been still less active than a sphere or a disc, although the knowledge is useful in many industrial fields, such as the designs for combustors, ventilator (2) − (8)

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Turbulence properties of an axisymmetric separation-and-reattaching flow

Cited by 21 publications

References 16 publications

Axial flow over a blunt circular cylinder with and without shear layer reattachment

Axial flow over a blunt circular cylinder with and without shear layer reattachment

Lattice Boltzmann method for axisymmetric turbulent flows

High-Reynolds-Number Flow past a Pipe

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