Separation mechanics of non-slender delta wings during streamwise gusts

Marzanek, Mathew; Rival, David E.

doi:10.1016/j.jfluidstructs.2019.07.001

Cited by 16 publications

(12 citation statements)

References 13 publications

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“…On low-aspect-ratio wings, because the flow is strongly three-dimensional, the circulation shed by the shear layer might roll up into a leading-edge vortex that remains steadily attached to the leading edge (Viola and Flay, 2011a,c;Viola et al, 2013aViola et al, , 2014Bot et al, 2014;Richards and Viola, 2015;Deparday et al, 2018;Arredondo-Galeana and Viola, 2018). The condition leading to the stability of leading-edge vortices on low-aspect-ratio wings is the objective of several recent studies including Maxworthy (2007); Widmann and Tropea (2015); Muir and Arredondo-galeana (2017); Akkala and Buchholz (2017); Marzanek and Rival (2019); and Eldredge and Jones (2019).…”

Section: Lifting Surfaces With a Sharp Leading Edgementioning

confidence: 99%

The force generation mechanism of lifting surfaces with flow separation

2021

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Section: Lifting Surfaces With a Sharp Leading Edgementioning

confidence: 99%

The force generation mechanism of lifting surfaces with flow separation

2021

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“…Figure 6( j – l ) presents the post-acceleration evolution () and highlights how quickly the flow returns to steady state. The strong FPG reduces cross-flow separation and even reattaches the 3-D separated flows (Marzanek & Rival 2019). However, in contrast with the hypothesis shown in figure 1( d ), the flow does not fully reattach for the present kinematics.…”

Section: Resultsmentioning

confidence: 99%

“…2017). ( d ) For an accelerating delta wing, the flow has been observed to reattach on the wing surface (Marzanek & Rival 2019). In contrast, for an accelerating prolate spheroid, a number of scenarios are possible: ( e ) the separation line will move closer to the model meridian centre or ( f ) a reattachment line will be created.…”

Section: Introductionmentioning

confidence: 99%

Dynamic separation on an accelerating prolate spheroid

Guo,

Kaiser,

Rival

2023

J. Fluid Mech.

Self Cite

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Time-varying flow separation on an accelerating prolate spheroid has been studied at various angles of incidence. Instantaneous pressure and scanning stereoscopic particle image velocimetry were used to shed light on the evolution of cross-flow structures for the Reynolds number ( $Re$ ) range of $1.0\times 10^6\leq Re \leq 1.5\times 10^6$ . The movement of separation lines is examined for various model accelerations to investigate on the interplay between acceleration and flow separation. The results demonstrate that for axial accelerations, the streamwise pressure distribution in the rear part of the prolate spheroid switches from an adverse to a favourable pressure gradient. At the same time, the circumferential adverse pressure gradient present during steady motion vanishes during said accelerations. In contrast, both streamwise and circumferential adverse pressure gradients strengthen when the model is axially decelerated. These dynamic pressure distributions influence the location of the separation line, which in turn moves closer to the model meridian during accelerations while moving outwards during decelerations. The streamwise vorticity distribution and the streamwise circulation both show how the separation-line position impacts the vortex formation. A high-vorticity region near the model surface is established during acceleration. In contrast, a decelerating model leads to transport of high-vorticity fluid into the outer area of the cross-flow separation. We further assess the memory effects following the near-impulsive velocity changes. The cross-flow retains the memory of moving separation lines shortly after the acceleration. However, the separation recovers quickly to a steady state.

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“…Viola et al (2014), Arredondo-Galeana and Viola (2018) and found conflicting results on whether a stable LEV can remain attached to the leading edge of spinnakers. This could be enabled, for example, by vorticity extraction through axial flow that balances the vorticity production at the leading edge (Akkala & Buchholz, 2017;Eldredge & Jones, 2019;Marzanek & Rival, 2019;Widmann & Tropea, 2015). A stable vortex is found, for example, on delta wings (Chang & Lei, 1996;Maxworthy, 2007), on the wing's outer region (hand wing) of some gliding birds such as the swift (Muir, Arredondo-Galeana, & Viola, 2017;Videler, Stamhuis, & Povel, 2004) and on autorotating seeds such as those of maples (Lentink, Dickson, van Leeuwen, & Dickinson, 2009).…”

Section: Introductionmentioning

confidence: 99%

Vortex flow of downwind sails

Arredondo-Galeana

Babinsky²,

Viola³

2023

Flow

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This paper sets out to investigate the vortex flow of spinnaker yacht sails, which are low-aspect-ratio highly cambered wings used to sail downwind. We tested three model-scale sails with the same sections but different twists over a range of angles of attack in a water tunnel at a Reynolds number of 21 000. We measured the forces with a balance and the velocity field with particle image velocimetry. The sails experience massively separated three-dimensional flow and leading-edge vortices convect at half of the free-stream velocity in a turbulent shear layer. Despite the massive flow separation, the twist of the sail does not change the lift curve slope, in agreement with strip theory. As the angle of attack and the twist vary, flow reattachment might occur in the time-average sense, but this does not necessarily result in a higher lift to drag ratio as the vorticity field is marginally affected. Finally, we investigated the effect of secondary vorticity, vortex stretching and diffusion on the vorticity fluxes. Overall, these results provide new insights into the vortex flow and associated force generation mechanism of wings with massively separated flow.

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Separation mechanics of non-slender delta wings during streamwise gusts

Cited by 16 publications

References 13 publications

The force generation mechanism of lifting surfaces with flow separation

The force generation mechanism of lifting surfaces with flow separation

Dynamic separation on an accelerating prolate spheroid

Vortex flow of downwind sails

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