Foliage motion under wind, from leaf flutter to branch buffeting
Foliage motion under wind, from leaf flutter to branch buffeting
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DOI：
10.1098/rsif.2018.0010
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发表时间：
2018-05
影响因子：
3.9
通讯作者：
L. Tadrist;M. Saudreau;P. Hémon;X. Amandolese;André Marquier;T. Leclercq;E. de Langre
中科院分区：
文献类型：
--
作者：
L. Tadrist;M. Saudreau;P. Hémon;X. Amandolese;André Marquier;T. Leclercq;E. de Langre
对于生物问题(光合作用、病原体发育或食草性)和更微妙的影响，如wi-fi传输或动物交流，风引起的树叶运动都是一种重要的现象。这样的树叶运动是支撑树叶的树枝的运动和树叶相对于树枝的运动的组合。单叶相对于枝条的动态和枝条的动态通常是分开研究的。在大型风洞中对整棵树的实验研究中，我们提出了第一个经验证据，即在低风速下，树叶的运动实际上是由单个树叶的颤振主导的，而在较高的风速下，树叶的运动实际上是由树枝的湍流抖动响应主导的。这两个区域之间的转换与叶片颤振对风速的弱相关性有关，而树枝的湍流抖振对风速的依赖性很强。与现有的基于工程的树叶和树枝运动模型的定量比较证实了这两种机制的普遍存在。对树上的风致阻力和树叶对光的拦截的同时测量表明，另一种机制--重组--的作用，即树叶弯曲和重叠，限制个别树叶的颤动。然后，我们讨论这些发现对风调节现象的作用的影响。
The wind-induced motion of the foliage in a tree is an important phenomenon both for biological issues (photosynthesis, pathogens development or herbivory) and for more subtle effects such as on wi-fi transmission or animal communication. Such foliage motion results from a combination of the motion of the branches that support the leaves, and of the motion of the leaves relative to the branches. Individual leaf dynamics relative to the branch, and branch dynamics have usually been studied separately. Here, in an experimental study on a whole tree in a large-scale wind tunnel, we present the first empirical evidence that foliage motion is actually dominated by individual leaf flutter at low wind velocities, and by branch turbulence buffeting responses at higher velocities. The transition between the two regimes is related to a weak dependence of leaf flutter on wind velocity, while branch turbulent buffeting is strongly dependent on it. Quantitative comparisons with existing engineering-based models of leaf and branch motion confirm the prevalence of these two mechanisms. Simultaneous measurements of the wind-induced drag on the tree and of the light interception by the foliage show the role of an additional mechanism, reconfiguration, whereby leaves bend and overlap, limiting individual leaf flutter. We then discuss the consequences of these findings on the role of wind-mediated phenomena.