Drag reduction by reconfiguration of highly flexible structures subjected to fluid flow

在大多数传统的工程应用中，结构被设计成刚性的，使得它们必须承受的载荷不会使它们显著变形。在自然界中，情况正好相反。特别是当涉及到流体载荷时，自然结构往往是顺应性和柔性的，而人造结构是刚性和不屈服的。植物寻求最大化其表面积以捕获最多的阳光，当它们受到流体负载（无论是水流还是风）时，通过改变它们的形状来利用它们的灵活性。我们说他们重新配置。**通过在流体负载下弯曲和扭曲，植物减少了垂直于流动的投影面积，并且也变得更加流线型。通过这两种主要的重构机制，植物必须支持的阻力载荷不会随着它们所经受的流速的平方而增长-就像在高雷诺数下刚性海崖体上那样-而是以不太明显的方式增长。** 水生和陆生植物重构的实验测量在文献中是丰富的，并且对于理解植物的阻力随流速的缩放存在很大的兴趣。然而，理论解释是很难从真实的植物，因为它们的复杂的几何形状和材料，以及标本之间的显着差异。正是由于这个原因，通过研究简单的结构，如梁和板受到流动的基本理解重构。我们试图通过风洞实验和数值模拟来获得简单弹性结构重构的基本理解。我们的目标是描绘一幅工厂重构的机械方面的全貌，包括其所有机制及其对阻力缩放的影响。**为了设计更好的模型来理解和预测风对森林、农作物和海岸植被的损害，以及研究水生和陆生植物对环境的适应，了解植被上的流体负荷是至关重要的。

In most traditional engineering applications, structures are designed to be stiff such that the loads they must bear do not deform them substantially. In nature, the contrary is true. Especially when it comes to fluid loading, natural structures tend to be compliant and flexible whereas man-made structures are rigid and unyielding. Plants, which seek to maximize their surface area to capture the most sunlight, make use of their flexibility by changing their shape when they are subjected to a fluid loading, whether water flow or wind. We say that they reconfigure.**By bending and twisting under fluid loading, plants reduce their projected area perpendicular to the flow, and also become more streamlined. Through these two primary mechanisms of reconfiguration, the drag load that plants must support does not grow with the square of the velocity of the flow they are subjected to - as it would on a rigid bluff body at a high Reynolds number - but rather in a less pronounced way. **Experimental measurements on the reconfiguration of aquatic and terrestrial plants are abundant in the literature, and a large interest exists for an understanding of the scaling of drag of plants with flow velocity. However, theoretical interpretation is difficult to obtain from real plants because of their complex geometries and materials as well as the significant variations between specimens. It is for this reason that a fundamental understanding of reconfiguration is sought by studying simple structures such as beams and plates subjected to flow. We seek to gain a fundamental understanding of the reconfiguration of simple elastic structures via wind tunnel experiments and numerical simulations. Our goal is to paint a complete picture of the mechanical aspects of plant reconfiguration with all its mechanisms and their effects on drag scaling.**It is essential to understand the fluid loadings on vegetation in order to devise better models to comprehend and predict wind damages to forests, crops and shore vegetation, as well as to study the adaptation of aquatic and terrestrial plants to their environment.********************