&lt;title&gt;Unsteady flow structure in the wake of the sphere&lt;/title&gt;

Leder, Alfred; Geropp, D.

doi:10.1117/12.150495

Cited by 12 publications

(8 citation statements)

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“…Two large-scale recirculation vortices formed downstream of the sphere are nearly symmetrical with respect to the wake centerline, even though instantaneous vortex structures are unsteady and irregular. These well defined circulating large-scale vortices dominate the flow structure in the near-wake downstream of the sphere, and these results are in a good agreement with those of other studies (Hadzic et al [2], Jang EFM11 and Lee [3], Leder and Geropp [4]). As it is seen from cross-comparison of the timeaveraged velocity fields <V> and vorticity contours <Z*>, distributions of the flow patterns clearly indicate that the wake flow area for the sphere without vent is smaller than that for the sphere with the vent.…”

Section: -P10supporting

confidence: 82%

Passive control of flow structure interaction between a sphere and free-surface

Özgören

Doğan

Okbaz

et al. 2012

EPJ Web of Conferences

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Section: -P10supporting

confidence: 82%

Passive control of flow structure interaction between a sphere and free-surface

Özgören

Doğan

Okbaz

et al. 2012

EPJ Web of Conferences

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“…These unique patterns of turbulent statistics reflect the wavy or helical turbulent structure of the wake in the cross-sectional planes behind the vortex formation region. Although the turbulent statistics of wavy wake structure in the streamwise plane have been investigated by several researchers (Sakamoto and Haniu 1990;Leder and Geropp 1993;Yun et al 2006), the helical structure of the sphere wake and its evolution in the cross-sectional planes have not been clearly described yet. The present PIV results of turbulent statistics in the cross-sectional planes are helpful to elucidate the ambiguity of helical structure and the evolution of the sphere wake.…”

Section: Resultsmentioning

confidence: 99%

POD analysis on the sphere wake at a subcritical Reynolds number

Jang

Lee

2010

J Vis

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Flow characteristics of turbulent wake behind a sphere at a subcritical flow regime were experimentally investigated. The particle image velocimetry measurements and proper orthogonal decomposition (POD) modal analysis were employed to get detailed flow information such as the wavy structure, swirling motion and coherent structures of the sphere wake. The variation of turbulent intensities of the radial and circumferential velocity components showed the swirling motion of sphere wake in the cross-sectional planes. The relative contribution of the POD mode 1, 2 and 3 in eigenvalues was 26, 11, and 8%, respectively. The general pattern of velocity fields for the POD mode 1 in the near-wake region of x/d = 0.7-1.4 is similar with that of time-averaged mean velocity fields. In addition, the sweeping flow in the region from x/d = 1.5 to x/d = 2.0 possesses wavy structure of the sphere wake. The experimental results of the present study would contribute to the fundamental understanding of the turbulent near-wake behind a sphere.

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“…4(b), the vertical turbulence intensity has the local maximum value at x/d =1.2 along the wake centerline (y = 0). Leder and Geropp (1993) Fig. 5.…”

Section: Resultsmentioning

confidence: 99%

“…The vortex-ring shaped protrusions are observed at Re = 11,000, which are very similar to those shown in the works of Werlé (1980) at Re = 16,000 and Yun et al (2006) at Re = 10,000. Meanwhile, Leder and Geropp (1993) observed the axisymmetric K-H instability at x/d ≈ 1.0, but the ring-type protrusions were not observed at Re = 10,000. In the visualization study of Hadzic et al (2002) at Re = 5 × 10 4 , the K-H instability occurred near x/d ≈ 0.6, and the laminar wake quickly changed into turbulent flow.…”

Section: Experimental Methodsmentioning

confidence: 99%

Visualization of turbulent flow around a sphere at subcritical reynolds numbers

Jang

Lee

2007

J Vis

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The shear layer evolution and turbulent structure of near-wake behind a sphere at Re = 11,000 and 5,300 were investigated using a smoke-wire visualization method. A laminar flow separation was found to occur near the equator. The smooth laminar shear layers appeared to be axisymmetrically stable to the downstream location of about x/d = 1.0 at Re = 11,000 and x/d = 1.7∼1.8 at Re = 5,300, respectively. At Re = 11,000, the vortex ring-shaped protrusions were observed with the onset of shear layer instability. Moreover, the transition from laminar to turbulence in the separated flow region occurred earlier at the hiher Reynolds number of Re = 11,000 than at Re = 5,300. The PIV measurements in the streamwise and cross-sectional planes at Re =11,000 clearly revealed the turbulent structures of the sphere wake such as recirculating flow, shear layer instability, vortex roll-up, and small-scale turbulent eddies.

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<title>Unsteady flow structure in the wake of the sphere</title>

Cited by 12 publications

References 0 publications

Passive control of flow structure interaction between a sphere and free-surface

Passive control of flow structure interaction between a sphere and free-surface

POD analysis on the sphere wake at a subcritical Reynolds number

Visualization of turbulent flow around a sphere at subcritical reynolds numbers

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