Flow‐induced reconfiguration of aquatic plants, including the impact of leaf sheltering
Flow‐induced reconfiguration of aquatic plants, including the impact of leaf sheltering
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DOI：
10.1002/lno.11542
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发表时间：
2020-06
影响因子：
4.5
通讯作者：
Xiaoxia Zhang;H. Nepf
中科院分区：
文献类型：
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作者：
Xiaoxia Zhang;H. Nepf
许多水生植物都很灵活，可以根据水流弯曲。这种重新配置可以通过减少正面面积和创建更流线型的形状来减少植物的阻力。先前的研究已经考虑了植物的浮力和刚性如何影响减阻。这项研究还考虑了重新配置如何影响植物叶子之间的遮挡，以及这反过来又如何影响植物的阻力。使用塑料 Rotala 盆景和活的假马齿苋，通过实验室实验和理论建模相结合，研究了单茎、有叶植物的姿态和阻力。实验室实验测量了单个植物在一定通道速度范围内的阻力和姿态。理论模型根据力平衡计算植物姿态和阻力，其中包括浮力、茎刚度引起的恢复力，以及经过修改以考虑叶子之间遮蔽的叶子阻力。叶子遮蔽的特征是遮蔽系数 Cs，它是植物姿态、叶角、叶距和叶宽的函数。 Cs 从 1 降至最小值 Cs0，与完全偏转的水平杆姿势相关。经过验证后，该模型被用来探索一系列叶子配置，并遵循在真实植物中发现的例子。建模和实验揭示了阻力随着重新配置而增加的条件，并且阻力达到水平杆姿势的有限极限值。这两种趋势在之前的重构模型中都没有被描述过。
Many aquatic plants are flexible and bend in response to current. This reconfiguration can reduce the drag on the plant, both by reducing the frontal area and by creating a more streamlined shape. Previous studies have considered how the buoyancy and rigidity of a plant impact the drag reduction. This study additionally considered how reconfiguration impacts the sheltering between leaves on a plant and how this, in turn, impacts the drag on the plant. The posture and drag of single‐stemmed, leaved plants were studied through a combination of laboratory experiments and theoretical modeling using both plastic Rotala bonsai and live Bacopa caroliniana. The laboratory experiments measured drag and posture on individual plants over a range of channel velocity. The theoretical model calculated plant posture and drag based on a force balance that included buoyancy, the restoring force due to stem stiffness, and leaf drag modified to account for sheltering between leaves. Leaf sheltering was characterized by a sheltering coefficient, Cs, which is a function of the plant posture, leaf angle, leaf spacing, and leaf width. Cs decreased from 1 to a minimum value, Cs0, associated with a fully deflected, horizontal stem posture. Once validated, the model was used to explore a range of leaf configurations, following examples found in real plants. The modeling and experiments revealed conditions for which drag increased with reconfiguration, and also that the drag reached a finite, limiting value for horizontal stem posture. Neither trend has been described in previous reconfiguration models.