Collaborative Research: Role of Turbulence Structure in Bedload Transport

合作研究：湍流结构在床质输送中的作用

• 批准号: 0124466
• 负责人: Mark Schmeeckle
• 金额: $ 10.31万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-15 至 2003-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0124466&HistoricalAwards=false
• 关键词: Collaborative; Research; Role; Turbulence; Structure

Sufficiently fast fluid flows over erodible beds of sand and gravel entrain surface particles, which then roll and hop along as bedload. This project aims to develop quantitative predictive relations between fluid flow and bedload transport that more precisely incorporate the role of the fluctuating flow velocities due to turbulence, which always is present. Such relations will apply to the non-uniform or unsteady flows that are ubiquitous in streams and beneath waves and will provide new insight into the formation of erosional and depositional sedimentary features from ripples and dunes to bars and channels to sorting and grading. The project will investigate (1) turbulence structure and bedload transport over simple bedforms such as bedload sheets and low dunes, (2) turbulence structure over abrupt streamwise changes in bed roughness, (3) turbulence structure and the fluctuating forces on fixed natural bed particles, (4) turbulence structure and the fluid forces that act on bedload particles during entrainment, and (5) the modification of fluid velocity and turbulence structure by moving bedload particles. In addition, the project will further develop our discrete-particle computational model for sediment transport by (1) incorporating into it better treatment of the lift forces on bed and bedload particles and of the reaction forces on the fluid as the particles accelerate and (2) coupling it with an existing numerical simulation of turbulent flow over three-dimensional bedforms. The proposed research addresses three intertwined issues: how the forces exerted on particles on the bed and moving over it are related to the temporal and spatial distribution of the near-bed fluid velocities, how the entrainment and motion of those particles are related to the forces, and how the near-bed fluid velocities are modified by the presence of the moving bedload.

足够快的流体流过沙子和砾石的侵蚀床，夹带表面颗粒，然后这些颗粒随着床负载滚动和跳跃。 该项目旨在开发流体流动和床质输送之间的定量预测关系，更精确地结合始终存在的湍流引起的波动流速的作用。 这种关系将适用于溪流中和波浪下普遍存在的不均匀或不稳定流，并将为从波纹和沙丘到沙坝和河道到分类和分级的侵蚀和沉积沉积特征的形成提供新的见解。 该项目将研究 (1) 简单地床形状（如床土片和低沙丘）上的湍流结构和床土输送，(2) 床面粗糙度沿流向突然变化的湍流结构，(3) 湍流结构和固定天然床颗粒上的脉动力，(4) 湍流结构和夹带过程中作用于床质颗粒的流体力，以及 (5) 通过移动床质颗粒来改变流体速度和湍流结构。 此外，该项目将进一步开发我们的沉积物输送离散颗粒计算模型，方法是（1）更好地处理河床和河床颗粒上的升力以及颗粒加速时流体上的反作用力和（2 ）将其与现有的三维地床湍流数值模拟相结合。 拟议的研究解决了三个相互交织的问题：施加在床上颗粒上并在其上移动的力如何与近床流体速度的时间和空间分布相关，这些颗粒的夹带和运动如何与力相关，以及移动床载的存在如何改变近床流体速度。