ENERGY EXCHANGE BETWEEN FLUID AND FLAPPING/BENDING STRUCTURES

具有长而柔韧的叶或茎的沉水植物常见于许多水生环境中，包括河流、湖泊和沿海海洋沃茨。这些植物对环境的生态健康和水质做出了许多重要贡献，包括作为庇护栖息地、食物来源、捕获和储存颗粒物、减少河床沉积物侵蚀和浊度。利用工程术语，水生植物可以被定义为复合的、各向异性的、粘弹性的、高度非均匀的结构。水生植物生活在流动的沃茨中，承受着复杂的载荷，这些载荷通常由拉伸、压缩、弯曲、扭转和剪切的混合物来表现。复杂和规模依赖的流体-植物相互作用仍然没有得到很好的理解。特别是，目前有关阻力生成和阻力控制机制的知识存在许多空白。 * 水生植物通常嵌入由各种边界（包括植物本身引入的边界）产生的多尺度边界层（BL）的叠加中。在河流和河口的边界层不同于典型的边界层。特别是，他们往往是深度有限的，他们有一个多尺度的结构，涉及床粗糙度的影响和内部的影响，植物边界在不同的尺度，如补丁，茎和叶。天然河流边界层的另一个重要特征是流动深度与粗糙度高度的比率较低，因此应谨慎使用描述它们的常规方法，例如应用对数流速剖面。*** * 在低淹没边界层中，水生植物受到流动的水施加的拖曳力。一个有趣的和未探索的流体-结构相互作用是弯曲的多个柔性体，而不是阻碍流动。这种情况是水生植物生命的一部分，它们的形态与它们必须忍受的生存流体流动密切相关。水生植物利用各种策略来最小化阻力。叶片折叠和植物形状流线型表示响应于变化的速度而不涉及波纹或颤振的静态重构的例子。动态重构是非线性相互作用的结果，导致颤振的出现，即使在固定的流速下也会不断改变设备的形状。虽然最近的实验研究集中在植物重构在流动的水，这一现象的理论和物理解释仍然没有得到很好的理解。本建议旨在推进国家的最先进的建模的柔性结构的流体-结构相互作用的边界层流动和波浪作用。通过实验和数值模拟研究了流体流动与柔性结构之间的能量交换。

Submerged plants with long, flexible leaves or stems are commonly found in many aquatic environments, including rivers, lakes and coastal marine waters. These plants make many significant contributions to the ecological health and water quality of their environments, including acting as sanctuary habitats, sources of food, capturing and storing particulates, reducing bed sediment erosion and turbidity. Using the engineering terminology, the aquatic plants can be defined as composite, anisotropic, viscoelastic, highly heterogeneous structures. Living in flowing waters, aquatic plants experience complex loads which are often presented by a mixture of tension, compression, bending, torsion and shear. The complex and scale dependent fluid-plant interactions are still not well understood. In particular, there are many gaps in the current knowledge related to drag-generating and drag control mechanisms.***   *Aquatic plants are typically embedded in a superposition of multi-scale boundary layers (BLs) generated by a variety of boundaries including those introduced by the plants themselves. BLs in streams and estuaries differ from the canonical boundary layers. In particular, they are often depth-limited, and they have a multi-scale structure involving effect of the bed roughness and internal effects of the plant boundaries at different scales such as patch, stem and leaf. Another important feature of natural stream BLs is a low ratio of flow depth to roughness height and therefore conventional approaches for their description, such as application of the logarithmic velocity profile, should be done with caution. ***   *In low-submergence boundary layers, aquatic plants experience drag forces imposed by the flowing water. An interesting and unexplored fluid-structure interaction is bending of multiple flexible bodies that are instead obstructing a flow. Such a situation is part of the life of aquatic plants whose morphologies are intimately related to the fluid flows they must endure to survive. Aquatic plants utilize various strategies to minimize the drag. Leaves folding and plant shape streamlining represent examples of the static reconfiguration in response to the changing velocity without involvement of waviness or flutter. Dynamic reconfiguration is a result of non-linear interactions leading to the appearance of flutter constantly changing the plant shape even at a fixed flow velocity. Although recent experimental studies have focused on the plant reconfiguration in flowing water,the theoretical and physical interpretations of this phenomenon are still not well understood. The present proposal is intended to advance the state-of-the-art modeling of the fluid structure interactions of flexible structures subjected to boundary layer flow and wave action. Experiments and numerical simulations are planned to study energy exchange between the fluid flow and flexible structures.