The rolling up of sheets in a steady flow

Schouveiler, Lionel; Boudaoud, Arezki

doi:10.1017/s0022112006000851

Cited by 48 publications

(69 citation statements)

References 10 publications

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“…31,[34][35][36][37] Analogous artificial systems were studied, including numerical models which reproduce experimental measurements on a fibre subjected to a soap film, 38,39 a flexible plate in air 40 or water 41,42 flow, and artificial leaves. 43,44 Experimental data are observed to collapse on a single reconfiguration curve so that…”

Section: -2 Barsu Et Almentioning

confidence: 99%

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Drag measurements in laterally confined 2D canopies: Reconfiguration and sheltering effect

et al. 2016

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Plants in aquatic canopies deform when subjected to a water flow and so, unlike a rigid bluff body, the resulting drag force F D grows sub-quadratically with the flow velocityŪ. In this article, the effect of density on the canopy reconfiguration and the corresponding drag reduction is experimentally investigated for simple 2D synthetic canopies in an inclinable, narrow water channel. The drag acting on the canopy, and also on individual sheets, is systematically measured via two independent techniques. Simultaneous drag and reconfiguration measurements demonstrate that data for different Reynolds numbers (400-2200), irrespective of sheet width (w) and canopy spacing (ℓ), collapse on a unique curve given by a bending beam model which relates the reconfiguration number and a properly rescaled Cauchy number. Strikingly, the measured Vogel exponent V and hence the drag reduction via reconfiguration is found to be independent of the spacing between sheets and the lateral confinement; only the drag coefficient decreases linearly with the sheet spacing since a strong sheltering effect exists as long as the spacing is smaller than a critical value depending on the sheet width. Published by AIP Publishing.

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Section: -2 Barsu Et Almentioning

confidence: 99%

“…4,38,42,43,45 However, in rivers, canopies are sets of plants close to each other, giving rise to a strong screening effect, so that plants in canopies do not behave like single plants. 46,47 There is also an increasing interest in theoretical models for drag force acting on poro-elastic systems.…”

Section: -2 Barsu Et Almentioning

confidence: 99%

Drag measurements in laterally confined 2D canopies: Reconfiguration and sheltering effect

et al. 2016

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“…Static and dynamic reconfiguration in response to increasing flow velocity often leads to deviation from a quadratic relationship between the drag and flow velocity, even at fairly high Reynolds numbers (e.g., Armanini et al 2005;Vogel 1989, 1994, 2009, Sand-Jensen 2003Statzner et al 2006). Despite plant leaves playing an important role in drag control at larger scales of patches and patch mosaics (e.g., Järvelä 2002;Wilson et al 2003), very little is known about the physical mechanisms involved (de Langre 2008;Ennos 1999;O'Hare et al 2010;Sand-Jensen 2003;Schouveiler et al 2006;Vogel 1989Vogel , 2009.…”

Section: Introductionmentioning

confidence: 99%

Flow-plant interactions at a leaf scale: effects of leaf shape, serration, roughness and flexural rigidity

et al. 2011

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The effects of leaf shape, serration, roughness and flexural rigidity on drag force imposed by flowing water and its time variability were experimentally studied in an openchannel flume at seven leaf Reynolds numbers ranging from 5 to 35 9 10 3 . The study involved artificial leaves of the same surface area but with three shapes ('elliptic', 'rectangular' and 'pinnate'), three flexural rigidities, smooth-edge and sawtooth-like serration, and three combinations of surface roughness (two-side rough, one-side rough/one-side smooth, and two-side smooth). Shape was the most important factor determining flow-leaf interactions, with flexural rigidity, serration and surface roughness affecting the magnitude but not the direction of the effect on drag control. The smoothedge elliptic leaf had a better hydrodynamic shape as it experienced less drag force, with the rectangular leaf showing slightly less efficiency. The pinnate leaf experienced higher drag force than the other leaves due to its complex geometry. It is likely that flow separation from 12 leaflets of the pinnate leaf prevented leaf reconfiguration such as leaflets folding and/or streamlining. Flexural rigidity strongly influenced the leaf reconfiguration and augmented the serration effect since very rigid leaves showed a strong effect of serration. Furthermore, serration changed the turbulence pattern around the leaves by increasing the turbulence intensity. Surface roughness was observed to enhance the drag force acting on the leaf at high Reynolds numbers. The results also suggest that there are two distinctly different flow-leaf interaction regimes: (I) regime of passive interaction at low turbulence levels when the drag statistics are completely controlled by the turbulence statistics, and (II) regime of active interaction at high turbulence levels when the effect of leaf properties on the drag statistics becomes comparable to the turbulence contribution.

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“…As Reynolds number (Re) was increased from 10 to 800, Zhu found that the exponents of the power laws decreased monotonically from approximately 2 towards 4/3. Schouveiler and Boudaoud (Schouveiler and Boudaoud, 2006) showed experimentally that flexible sheets with rigid tethers can roll up into cone shapes in steady flow, also reducing the drag acting upon them. Gosselin et al (Gosselin et al, 2010) considered flexible plates with rigid tethers in a steady wind tunnel.…”

Section: Introductionmentioning

confidence: 99%

Reconfiguration and the reduction of vortex-induced vibrations in broad leaves

Miller

Santhanakrishnan

Jones

et al. 2012

Journal of Experimental Biology

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SUMMARYFlexible plants, fungi and sessile animals reconfigure in wind and water to reduce the drag acting upon them. In strong winds and flood waters, for example, leaves roll up into cone shapes that reduce drag compared with rigid objects of similar surface area. Less understood is how a leaf attached to a flexible leaf stalk will roll up stably in an unsteady flow. Previous mathematical and physical models have only considered the case of a flexible sheet attached to a rigid tether in steady flow. In this paper, the dynamics of the flow around the leaf of the wild ginger Hexastylis arifolia and the wild violet Viola papilionacea are described using particle image velocimetry. The flows around the leaves are compared with those of simplified physical and numerical models of flexible sheets attached to both rigid and flexible beams. In the actual leaf, a stable recirculation zone is formed within the wake of the reconfigured cone. In the physical model, a similar recirculation zone is observed within sheets constructed to roll up into cones with both rigid and flexible tethers. Numerical simulations and experiments show that flexible rectangular sheets that reconfigure into U-shapes, however, are less stable when attached to flexible tethers. In these cases, larger forces and oscillations due to strong vortex shedding are measured. These results suggest that the three-dimensional cone structure in addition to flexibility is significant to both the reduction of vortex-induced vibrations and the forces experienced by the leaf. Supplementary material available online at

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The rolling up of sheets in a steady flow

Cited by 48 publications

References 10 publications

Drag measurements in laterally confined 2D canopies: Reconfiguration and sheltering effect

Drag measurements in laterally confined 2D canopies: Reconfiguration and sheltering effect

Flow-plant interactions at a leaf scale: effects of leaf shape, serration, roughness and flexural rigidity

Reconfiguration and the reduction of vortex-induced vibrations in broad leaves

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