Dye visualization near a three-dimensional stagnation point: application to the vortex breakdown bubble

Brøns, Morten; Thompson, Mark C.; Hourigan, Kerry

doi:10.1017/s0022112008005107

Cited by 13 publications

(13 citation statements)

References 39 publications

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“…Thompson & Hourigan (2003) showed that small errors in the rotating end-cover produced surprisingly strong asymmetries in the flow, a finding supported with fully three-dimensional numerical simulations in Brons et al (2007). Further work showed that the accuracy of injection of visualization dye in experiments was itself sufficient to give rise to asymmetric flow (Brons, Thompson & Hourigan 2009). …”

Section: Resultsmentioning

confidence: 71%

Effect of small asymmetries on axisymmetric stenotic flow

et al. 2013

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Flow through axisymmetric and eccentric sinuous stenoses is investigated numerically, for Reynolds numbers up to 400. The eccentricity consists of an offset of the stenosis throat. A range of stenosis eccentricity is tested; the wake flow is found to be highly sensitive to small eccentricities in the stenosis geometry, even with stenosis offsets of the order of the machining precision of experimental test-sections. Comparisons are made between the numerically simulated flow through stenoses with small eccentricities and results from the literature of non-axisymmetric flows through nominally axisymmetric geometries. The effect of distortion to the inlet Poiseuille velocity profile is also investigated and found to have a significantly less severe effect on the downstream wake flow than geometric eccentricity.

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Section: Resultsmentioning

confidence: 71%

Effect of small asymmetries on axisymmetric stenotic flow

et al. 2013

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“…These asymmetries are due to flow structural instability and experimental imperfections in the location of the injection hole and in the alignment of the rotating top disk. 38,40,41 At late stages, the dye slowly fills the two bubbles and becomes thicker due to the molecular diffusion ͓see Fig. 4͑c͔͒.…”

Section: Vortex Breakdown Visualization With Neutrally Buoyant Dmentioning

confidence: 99%

Experimental control of vortex breakdown by density effects

Ismadi¹,

Meunier²,

Fouras³

et al. 2011

Physics of Fluids

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International audienceThe vortex breakdown inside a cylinder with a rotating top lid is controlled experimentally by injecting at the bottom a fluid with a small density difference. The density difference is obtained by mixing a heavy dye or alcohol with water in order to create a jet denser or lighter than water. The injection of a heavy fluid creates a buoyancy force downward, which counteracts the meridional recirculation in the cylinder and thus enhances the formation of a vortex breakdown bubble. The stability diagram shows that even a very small density difference of 0.02% is able to decrease by a factor of 2 the critical Reynolds number of appearance of the breakdown. On the other hand, the injection of a lighter fluid does not destroy the vortex breakdown. However, for large enough density differences (larger than 0.03%), the lighter fluid is able to pierce through the bubble and leads to a new structure of the vortex breakdown. Finally, a parallel is drawn between a light jet and a vortex ring generated at the bottom of the cylinder: strong vortex rings are able to pierce through the bubble, whereas weak vortex rings are simply advected around the bubble

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“…Experiments and calculations have indicated that very slight asymmetries in the TDC geometry, i.e., very slight structural asymmetries, can lead to clearly asymmetric flows. 32,33 In addition, slight visualisation technique asymmetries, such as slight misalignments in dye injection 34 and dye diffusion 35 can lead to strongly asymmetric visualisations even for strictly symmetric flows. The onset of precession of the breakdown bubbles in the TDC has, however, been observed for high Reynolds numbers 36,37 and at cylinder aspect ratios above 3.3, asymmetry has also been observed.…”

Section: Introductionmentioning

confidence: 99%

A study of the geometry and parameter dependence of vortex breakdown

2015

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The types of vortex breakdown observed in the torsionally driven cylinder (TDC) flow and in the flow through an open-ended pipe are compared. The connection between the various breakdown types is specifically addressed, and the differences in manifestation of breakdown are attributed to the different Reynolds number regimes involved. Here, in both cases, the Reynolds number is based on quantities associated with the vortex core immediately upstream of breakdown, rather than the more geometry-specific Reynolds number defined in the previous work. Thus, the relationship between the TDC flow and the flows observed in other, more open geometries, is clarified. The predominantly asymmetric breakdown observed in open high Reynolds number flows is replaced by a closed bubble form with decreasing Reynolds number in the TDC. Three-dimensional numerical simulations support this interpretation, showing that the 3D spiral type of breakdown is replaced by a TDC-type axisymmetric breakdown in an open pipe as the Reynolds number is reduced. The stability of the three-dimensional solutions indicates that spiral breakdown modes stabilise at lower Reynolds number, leading to an axisymmetric breakdown state as a stable evolved flow solution. C 2015 AIP Publishing LLC.

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Dye visualization near a three-dimensional stagnation point: application to the vortex breakdown bubble

Cited by 13 publications

References 39 publications

Effect of small asymmetries on axisymmetric stenotic flow

Effect of small asymmetries on axisymmetric stenotic flow

Experimental control of vortex breakdown by density effects

A study of the geometry and parameter dependence of vortex breakdown

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