COLLABORATIVE RESEARCH: The statistical mechanics of bed load sediment transport: Meshing theory, experiments and advanced computations of coupled fluid-particle behavior

合作研究：床载沉积物迁移的统计力学：耦合流体-颗粒行为的网格理论、实验和高级计算

• 批准号: 1226288
• 负责人: Mark Schmeeckle
• 金额: $ 24.98万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2017-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1226288&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; statistical; mechanics; bed

Probabilistic descriptions of particle motions, borrowing key ideas from statistical mechanics, offer a compelling strategy for connecting statistical descriptions of particle motions with dynamical formulations of coupled fluid-particle behavior. This research is aimed at incorporating this style of analysis in studies of bed load sediment transport, growing the connection between small-scale mechanistic descriptions of transport and larger-scale problems of river morphodynamics and tracer motions. The work involves: (1) formally defining an ensemble of particle configurations and velocities in a manner similar to formulations from classic statistical mechanics, notably to clarify effects of active particle patchiness in calculating transport rates; (2) pursuing a theoretical formulation of the exponential-like distribution of particle velocities from statistical-mechanics arguments; (3) pursuing a set of physical and computational experiments designed to fully clarify the relationship between the particle diffusivity and the ensemble-average particle velocity; (4) using our numerical sediment transport modeling system, the first discrete-particle transport model to have four-way coupling (mass and momentum exchange between the solids and fluid), to explore detailed mutual interactions between turbulence structures and sediment motions; and (5) pursuing theoretical, experimental and computational work focused on the effects of covariance in particle activities and velocities in computing sediment fluxes, and the spatiotemporal organization of motions of mixed particle sizes in response to turbulence.The negative consequences of human modifications to rivers, such as by dams, irrigation withdrawal, and mining activities, remain difficult to forecast and mitigate. This is partly because current understanding of sediment movement remains insufficient to predict many of the river bed geometric changes, and the transport and fate of contaminated river sediments that occur during varying river discharges. The work is aimed at elaborating a theoretical framework, informed by experiments and advanced computations, for describing the transport of bed load sediment, tracer particles, and sediment-borne substances. The work will clarify how flow turbulence and the associated patchiness in particle entrainment and deposition contribute to variability in transport rates. The probabilistic basis of the theory, together with the advanced computations of coupled fluid-particle systems, represents an important melding of techniques for understanding the physics of sediment transport. In addition, the work involves: (1) a collaborative structure of student education that will greatly enrich the intellectual experiences of students from two universities; (2) developing compelling teaching tools deriving from visualizations of experiments and numerical simulations; and (3) providing one-of-a-kind data sets to the science community.

粒子运动的概率描述借用了统计力学的关键思想，提供了一种令人信服的策略，将粒子运动的统计描述与流体-粒子耦合行为的动力学公式联系起来。 这项研究的目的是将这种分析方式纳入床载沉积物输运研究中，增强输运的小规模机械描述与河流形态动力学和示踪运动的更大规模问题之间的联系。 这项工作包括：（1）以类似于经典统计力学公式的方式正式定义粒子构型和速度的集合，特别是为了阐明活性粒子斑块在计算传输速率时的影响； (2) 从统​​计力学论证中寻求粒子速度指数分布的理论表述； (3) 进行一系列物理和计算实验，旨在充分阐明粒子扩散率与系综平均粒子速度之间的关系； （4）使用我们的数值沉积物输运建模系统，第一个具有四向耦合（固体和流体之间的质量和动量交换）的离散粒子输运模型，来探索湍流结构和沉积物运动之间的详细相互作用； (5) 进行理论、实验和计算工作，重点关注颗粒活动和速度的协方差在计算沉积物通量中的影响，以及混合颗粒尺寸运动响应湍流的时空组织。人类对河流的改造（例如水坝、灌溉撤水和采矿活动）的负面影响仍然难以预测和减轻。 部分原因是目前对沉积物运动的了解仍然不足以预测许多河床几何变化，以及在不同河流排放过程中发生的受污染河流沉积物的运输和归宿。 这项工作的目的是通过实验和高级计算来阐述一个理论框架，用于描述床载沉积物、示踪颗粒和沉积物中的物质的传输。 这项工作将阐明流动湍流以及颗粒夹带和沉积中的相关斑块如何影响传输速率的变化。 该理论的概率基础与耦合流体-粒子系统的高级计算一起，代表了理解沉积物迁移物理学的技术的重要融合。 此外，工作还包括：（1）学生教育的协作结构，将极大地丰富两所大学学生的智力经历； (2) 开发源自实验可视化和数值模拟的引人注目的教学工具； (3) 向科学界提供独一无二的数据集。