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

由于数以万计的水坝的建设和现在的退役，以及影响河流流量的用水和土地利用的变化，美国的溪流和河流处于不断变化的状态。广泛的实地研究记录了砾石河床的几何形状和底质的复杂变化对鱼类和其他生物群的影响。由于湍急的河流携带的沙砾的运动具有斑块性和间歇性，目前的泥沙运输模型无法预测大多数这些关键的河岸变化。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，在单个颗粒和湍流漩涡的水平上调查和描述沉积物运动。统计物理原理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，该框架有望提供预测能力，从而为该国水道发生的巨大变化提供政策指导。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粒子运动分布决定。实验室实验将由粒子和湍流解决超级计算机模拟耦合动量复制。这项工作还旨在为交替沙洲形成的情况参数化统计理论，从而为进一步阐明存在零星、稀薄运输条件的渠道尺度形态动力学问题提供基础。该奖项由地貌与土地利用动态计划和国家战略计算计划共同资助。

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.