Vortex Interactions with Walls

Doligalski, T. L.; Smith, Charles R.; Walker, James D.

doi:10.1146/annurev.fl.26.010194.003041

Cited by 343 publications

(94 citation statements)

References 31 publications

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“…In the hypothetical inviscid case (ν = 0), the ring diameter would increase indefinitely, with the core positions gradually moving closer to the boundary. 31 However, the observed behaviour (for ν = 0) is notably different from this, as illustrated by Fig. 5(d), where the white crosses have been included to show the trajectory of the ring core during this period of the impact.…”

Section: A Interaction Characteristicsmentioning

confidence: 85%

“…Several of the key features discussed here are similar to those observed when a vortex ring interacts with a solid-wall boundary, which has been studied previously by Walker et al, 29 and related articles. 30,31 Figure 5 shows a sequence of images taken at different stages during a typical impact (see caption for details). Here, the internal structure of the vortex ring has been made visible using fluorescent dye and a vertical light sheet to illuminate the mid-plane of the ring's trajectory.…”

Section: A Interaction Characteristicsmentioning

confidence: 99%

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The interaction of a vortex ring with a sloped sediment layer: Critical criteria for incipient grain motion

Munro

2012

Physics of Fluids

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Experiments were performed to analyse the interaction between a vortex ring and a sloped sediment layer. Attention focussed on interactions under “critical” conditions, in which sediment motion was only just induced by the ring's flow field. Both hydraulically smooth and hydraulically rough bedforms were analysed, using near-spherical monodisperse sediments with relative densities of 1.2 and 2.5 and mean diameters (dp) ranging between 80 and 1087 μm. Measurements of the vortex-ring flow field were obtained, during the interaction, using two-dimensional particle imaging velocimetry. The threshold conditions for incipient sediment motion were analysed in terms of the critical Shields parameter (Nc), defined in terms of the peak tangential velocity measured adjacent to the bed surface. Bed-slope effects were investigated by tilting the sediment layer at various angles between the horizontal and the repose limit for the sediment. In all cases, the propagation axis of the vortex ring was aligned normal to the bed surface. The measured values of Nc were compared with a force-balance model based on the conditions for incipient grain motion on a sloping bed. For hydraulically smooth bedforms, where the bed roughness is small compared to the boundary-layer depth, the model was derived to account for how viscous stresses affect the drag and lift forces acting on the near surface sediment. For hydraulically rough bedforms, where this viscous-damping effect is not present, the model assumes the drag and lift forces scale with the square of the near-bed (inviscid) velocity scale. In both cases, the model predicts that bedforms become more mobile as the bed slope is increased. However, the damping effect of the viscous sublayer acts as a stabilizing influence for hydraulically smooth bedforms, to reduce the rate at which the bed mobility increases with bed slope. The measured values of Nc were in agreement with the trends predicted by this model, and exhibit a transition in behaviour between the smooth-bed and rough-bed cases when dp/δs ≈ 20 (where δs is the viscous-sublayer length scale).

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Section: A Interaction Characteristicsmentioning

confidence: 85%

Section: A Interaction Characteristicsmentioning

confidence: 99%

The interaction of a vortex ring with a sloped sediment layer: Critical criteria for incipient grain motion

Munro

2012

Physics of Fluids

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“…For a sufficiently high Reynolds number vorticity from the boundary layer is ejected into the surrounding fluid, resulting in secondary vortex structures. This phenomenon has been denoted eruption of the boundary layer [1,2], unsteady separation [3,4] or bursting [5], and it occurs for a wide range of Reynolds numbers [6,7]. The interaction between concentrated vorticity in a fluid and the vorticity created at a no-slip wall occurs in many important settings.…”

Section: Introductionmentioning

confidence: 99%

Codimension three bifurcation of streamline patterns close to a no-slip wall: A topological description of boundary layer eruption

et al. 2015

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A vortex close to a no-slip wall gives rise to the creation of new vorticity at the wall. This vorticity may organize itself into vortices that erupt from the separated boundary layer. We study how the eruption process in terms of the streamline topology is initiated and varies in dependence of the Reynolds number Re. We show that vortex structures are created in the boundary layer for Re around 600, but that these disappear again without eruption unless Re > 1000. The eruption process is topologically unaltered for Re up to 5000. Using bifurcation theory, we obtain a topological phase space for the eruption process, which can account for all observed changes in the Reynolds number range we consider. The bifurcation diagram complements previously analyzes such that the classification of topological bifurcations of flows close to no-slip walls with up to three parameters is now complete.

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“…Such a vortex may occur in the boundary layer approaching a surface-mounted obstacle, i.e. a juncture flow, vortices shed from upstream surfaces, coherent vortex structures occurring in turbulent boundary layers, and branching pipes and vessels [10]. A particularly interesting application that brings together a number of these effects is the interaction of a rotor-tip vortex with a helicopter airframe.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, it is an area for which the authors have collaborated with FTS and/or made complementary contributions. The paper also serves as a review of this important field and can be considered to be an update of the excellent review by Doligalski et al [10]. Subsequent sections recount the developments in the asymptotic theory of unsteady separation, stability of separating flows, and recent work on better understanding unsteady separation through solutions of the full Navier-Stokes equations.…”

Section: Introductionmentioning

confidence: 99%

Unsteady separation in vortex-induced boundary layers

Cassel

Conlisk

2014

Phil. Trans. R. Soc. A.

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This paper provides a brief review of the analytical and numerical developments related to unsteady boundary-layer separation, in particular as it relates to vortex-induced flows, leading up to our present understanding of this important feature in high-Reynolds-number, surface-bounded flows in the presence of an adverse pressure gradient. In large part, vortex-induced separation has been the catalyst for pulling together the theory, numerics and applications of unsteady separation. Particular attention is given to the role that Prof. Frank T. Smith, FRS, has played in these developments over the course of the past 35 years. The following points will be emphasized: (i) unsteady separation plays a pivotal role in a wide variety of high-Reynolds-number flows, (ii) asymptotic methods have been instrumental in elucidating the physics of both steady and unsteady separation, (iii) Frank T. Smith has served as a catalyst in the application of asymptotic methods to high-Reynolds-number flows, and (iv) there is still much work to do in articulating a complete theoretical understanding of unsteady boundary-layer separation.

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Vortex Interactions with Walls

Cited by 343 publications

References 31 publications

The interaction of a vortex ring with a sloped sediment layer: Critical criteria for incipient grain motion

The interaction of a vortex ring with a sloped sediment layer: Critical criteria for incipient grain motion

Codimension three bifurcation of streamline patterns close to a no-slip wall: A topological description of boundary layer eruption

Unsteady separation in vortex-induced boundary layers

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