COLLABORATIVE RESEARCH: The statistical mechanics of bed load sediment transport: Scaling particle motion to fluvial form

美国的河流和河流处于流动状态，原因是建造了数万座水坝，现在正在退役，以及影响河流流量的水和土地利用的变化。广泛的实地研究证明，砾石河床河流的几何形状和底物发生了复杂的变化，影响了鱼类和其他生物群。由于湍动河流携带的沙石运动具有斑驳、间歇的性质，目前的泥沙输送模型无法预测这些关键的河岸变化中的大多数。该项目使用基于物理的超级计算机算法和先进的实验室成像技术，在单个颗粒和湍流涡流的水平上调查和描述沉积物的运动。统计物理原理被应用于这些超级计算机和实验室结果，以产生一个理论框架，预计将提供预测能力，从而为国家水道发生的剧烈变化提供政策指导。实验工作涉及砾石床水槽和高速视频，以说明河床地形变化的基础，以及该问题中的特征长度尺度如何由颗粒运动的分布确定。实验室实验将通过结合动量的粒子和湍流分辨超级计算机模拟来复制。这项工作还旨在将交替沙洲形成情况下的统计理论参数化，从而为进一步澄清存在零星稀薄运输条件的河道尺度地貌动力学问题提供基础。该奖项由地貌和土地利用动力学计划和国家战略计算倡议共同资助。

The streams and rivers of the United States are in a state of flux due to the building, and now decommissioning, of tens of thousands of dams, as well as changes in water use and land use influencing river flows. Extensive field studies have documented complex changes to the geometry and substrate of gravel-bedded rivers affecting fish and other biota. Due to the patchy, intermittent nature of the motion of sand and gravel carried by turbulent river flow, current models of sediment transport are unable to predict most of these critical riparian changes. This project investigates and describes sediment motion at the level of individual grains and turbulent eddies using physics-based supercomputer algorithms and advanced laboratory imaging techniques. Statistical physical principles are applied to these supercomputer and laboratory results to produce a theoretical framework that is expected to provide predictive capabilities, and thus, policy guidance regarding dramatic changes occurring in the country's waterways.The experimental work involves gravel-bed flumes and high-speed video to illustrate the basis for changes in streambed topography, and how the characteristic length-scales in this problem are determined by the distribution of particle motions. Laboratory experiments will be replicated by particle- and turbulence-resolving supercomputer simulations coupled in momentum. The work also is aimed at parameterizing statistical theory for the case of alternate bar formation, thus providing the basis for further clarifying channel-scale morphodynamics problems in which patchy, rarefied transport conditions exist.This award is cofunded by the Geomorphology and Land-use Dynamics Program and the National Strategic Computing Initiative.