CAREER: Multiscale Turbulent Flow Interaction with Flexible Branched Trees for Storm Impact Research

这项研究的目的是系统地研究树冠的流体-结构相互作用和树冠上的湍流，为改进对风暴严重程度的预测铺平道路。树冠上有灵活的树枝，可以变形并动态适应非稳定的湍流，并不断与大气交换空气。关于相干流动结构的形成及其与树冠结构和树木特征的联系，仍然存在重大的悬而未决的问题。将研究树冠和大尺度湍流相干之间的多尺度相互作用，以填补目前关于树冠上湍流流动知识的一个关键空白，并确定控制风暴严重程度的过程，也是全球生物地球化学循环和气候变化的关键因素。主要的教育目标是加强机械工程专业学生的多学科教育，提高少数民族本科生的保留率。以自然为灵感的例子和现场演示将被用来激励学生攻读科学和工程学科。一个紧密整合的外展计划将被开发出来，以增加公众对树冠内风的流体动力学、其在风暴中的作用以及对气候变化的相关影响的了解。拟议的研究使用灵活的多枝树和具有旋转能力的风洞来研究灵活的树冠上的湍流相互作用。大涡模拟和树枝从树叶到树干的动态多链接模型将被用来形成湍流和分形树的多尺度相互作用模型，并确定以前未知的负责大气和树冠之间动量和能量转移的物理机制。研究树枝风致偏转、树枝振动引起的气动阻尼和湍流非定常流动之间的反馈过程，以解释树冠呼吸在抛射(爆发)和扫掠(阵风)湍流阶段的过程，并找出这两个阶段不同的时空输送特征的来源。这一结果将被用于预测线性耦合技术，以研究在树冠中观察到的渐进变形波和流动相干结构。这项研究工作的预期结果是对令人费解的树冠流动观测结果的解释，以及对恶劣天气条件下湍流结构的改进预测。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this research is to systematically investigate the fluid-structure interactions of a tree canopy and the turbulent flow over the canopy, paving the way to improved predictions of storm severity. The canopy has flexible branched trees that deform and dynamically adapt to unsteady turbulent flow and continuously exchanges air with the atmosphere. There are still significant open questions about the formation of coherent flow structures and their connection to the canopy architecture and tree characteristics. The multiscale interactions between the tree canopy and large-scale turbulent coherent will be studied to fill a critical gap in the current knowledge about turbulent flow over canopies and to identify the processes that control storm severity and are also critical factors in global biogeochemical cycles and climate change. The primary educational objective is to enhance the multidisciplinary education of Mechanical Engineering students and increase the retention rate of minority undergraduate students. Nature-inspired examples and live demonstrations will be used to motivate students to pursue science and engineering disciplines. A tightly integrated outreach program will be developed to increase public knowledge about the fluid dynamics of wind in canopies, its role in storms, and the associated impacts on climate change.The proposed research uses flexible multi-branch trees and a wind tunnel with rotational capabilities to study turbulent flow interactions above flexible tree canopies. Large-eddy simulations and a dynamic multilink model of branched trees from foliage to the trunk will be used to form a multiscale interaction model of the turbulent flow and a fractal tree and to identify the previously unknown physical mechanisms responsible for momentum and energy transfers between atmosphere and tree canopies. The feedback process between wind-induced deflection of a branched tree, aerodynamic damping due to branch oscillation and turbulent unsteady flow will be investigated to explain the process of the canopy breathing during ejection (burst) and sweep (gust) turbulent phases and to find the origin of distinct spatial and temporal transport features during these phases. The results will be used in a predictive linear coupled technique to study progressive deformation waves and flow coherent structures observed in canopies. An expected outcome of this research effort is an explanation for the puzzling observations of canopy flows and improved predictions of turbulent structures in detrimental weather conditions such as wind storms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.