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: 1226076
• 负责人: David Furbish
• 金额: $ 20.74万
• 依托单位: Vanderbilt 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 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1226076&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.

粒子动作的概率描述，从统计力学中借用关键思想，为将粒子运动的统计描述与耦合流体粒子行为的动态配方联系起来提供了令人信服的策略。 这项研究旨在将这种分析方式纳入床负荷沉积物传输的研究中，从而增加了传输的小规模机械描述与河流形态动力学和示踪剂运动的大规模问题之间的联系。 这项工作涉及：（1）以类似于经典统计力学的制剂的方式正式定义粒子构型和速度的集合，特别是为了阐明主动粒子斑点在计算传输速率中的影响； （2）从统计机械论证中追求粒子速度的指数状分布的理论表述； （3）追求一组物理和计算实验，旨在充分阐明粒子扩散率与集合平均粒子速度之间的关系； （4）使用我们的数值沉积物传输建模系统，这是第一个离散的粒子传输模型，它具有四向耦合（固体和流体之间的质量和动量交换），以探索湍流结构与沉积物运动之间的详细相互作用； （5）追求理论，实验和计算工作集中在粒子活动和速度中的协方差在计算沉积通量中的影响，以及混合粒径运动的时空组织响应湍流。对河流的负面影响，对河流的负面影响，例如，由大坝，灌溉戒断，以及抑制性，仍然很难进行灌溉，以及仍然难以撤离，并保持较难。 这部分是因为当前对沉积物运动的理解仍然不足以预测许多河床的几何变化，以及在不同河流排放期间发生的受污染河流沉积物的运输和命运。 这项工作旨在详细阐述一个理论框架，该框架通过实验和高级计算，以描述床负荷沉积物，示踪剂颗粒和沉积物 - 传播物质的运输。 这项工作将阐明流动湍流以及颗粒夹带和沉积的相关斑块如何导致运输速率的变异性。 该理论的概率基础，以及耦合流体粒子系统的先进计算，代表了了解理解沉积物传输物理的技术的重要融合。 此外，这项工作涉及：（1）学生教育的协作结构，将大大丰富两所大学的学生的智力经历； （2）开发从实验和数值模拟的可视化源性的引人入胜的教学工具； （3）为科学界提供一种独一无二的数据集。