Flow induced particle movement under smooth to rough boundary conditions: A force-time history formulation

该研究将探讨在波动水动力的影响下，从水力光滑到完全粗糙的边界，以及从层流到完全湍流的流动条件下的沉积物迁移。目前，平均边界切应力被广泛用作确定流中颗粒运动阈值的标准，以及生物和工业流。不幸的是，这些流动的动态特征没有被这些标准充分捕获，甚至也没有被基于瞬时水动力的模型捕获。也就是说，这些方法忽略了流动的时间依赖性动态方面（最近由Diplas，Dancey等人（2008）证明）。在这项研究中的基本前提是，脉动力和相关的冲动，由于湍流的高度不稳定和动态的性质，以及颗粒诱导的旋涡脱落的层流和湍流的情况下，负责在近阈值条件下的泥沙输运。这项研究将调查流动结构的缩放行为，这是最有效的给予必要的冲动。这将通过实验来实现，使用最先进的时间分辨（1000 kHz）的数字粒子图像测速仪测量动态颗粒表面压力测量和非侵入式颗粒运动检测的同时。 智力优点：可侵蚀边界上的水流是地球表面动力学中的中心问题，并适用于生物流动和许多工业过程。这一过程很复杂，而且人们仍然知之甚少。这项研究的智力价值涉及我们知识的进步和对现象的理解以及实际的预测能力。这项研究将：推进我们对波动流体力和颗粒移位之间的动态相互作用的基本理解，并可能有助于新的分析方法和实验方法的发展，以及，确定在赋予足够的动量/脉冲夹带颗粒方面最有效的流动结构，有助于发展一种新的通用标准，用于确定运动条件的阈值，促进改进的推移质输沙方程的发展，特别是那些使用超剪应力概念的推移质输沙方程。更广泛的影响：该研究涉及与地球临界区和各种工业过程相关的广泛的社会问题，其中包括：1。环境中的水过程动力学。改进现有的稳定水道设计工程方法。发现桥墩和其他结构物周围冲刷的机理。建立基于风险的方法，防止污染沉积物的清除。确定对河流生态和生物的影响2。气候变化和自然灾害。水库淤积影响预测及寿命预测。识别海滩侵蚀机制和实施有效的保护计划3.工业加工。改进的管道固相输运模型的发展。建立更好的固相污染物去除（冲洗）模型。

The research will explore sediment dislodgement under the influence of fluctuating hydrodynamic forces for boundaries spanning hydraulically smooth to fully-rough, and flow conditions from laminar to fully turbulent. At the present time, the mean boundary shear stress is widely used as the criterion for identifying the threshold of motion for particles in streams, as well as biological and industrial flows. Unfortunately, the dynamic features of these flows are not adequately captured by such criteria, nor even by models based upon instantaneous hydrodynamic forces. That is, these approaches ignore the time-dependent dynamic aspects of the flow (recently demonstrated by Diplas, Dancey et al. (2008).) The basic premise in this study is that fluctuating forces and associated impulse due to the highly unsteady and dynamic nature of turbulent flow, and grain-induced vortex shedding for both the laminar and turbulent cases, are responsible for sediment transport at near threshold conditions. The research will investigate the scaling behavior of flow structures which are most effective at imparting the necessary impulse. This will be accomplished experimentally, using state-of-the- art time-resolved (1000 kHz) digital particle image velocimeter measurements simultaneous with dynamic grain surface pressure measurements and non-intrusive grain motion detection. Intellectual merit: Flow over an erodible boundary is the central problem in earth surface dynamics and is applicable to biological flows and many industrial processes. The process is complex and still poorly understood. The intellectual merit of this research relates to both the advancement of our knowledge and understanding of the phenomena as well as practical predictive capabilities. This research will: Advance our fundamental understanding of the dynamic interplay between fluctuating fluid forces and particle dislodgement and may contribute to the development of new analytical approaches and experimental methods, as well, Identify the flow structures that are most effective in imparting sufficient momentum/impulse to entrain particles, Contribute to the development of a new universal criterion for identifying threshold of motion conditions, Facilitate the development of improved bed load transport equations, especially those using the notion of excess shear stress. Broader Impact: The research relates to a broad range of societal problems associated with the Earth's Critical Zone and various industrial processes, among them: 1. Dynamics of water processes in the environment. Improvement of existing engineering methods for the design of stable waterways. Discovery of the mechanisms responsible for scour around bridge piers and other structures. Establishment of risk-based methods for preventing the removal of contaminated sediments. Identification of consequences on stream ecology and biology 2. Climate change and Natural Hazards. Prediction of effects on reservoir sedimentation and its life expectancy. Identification of beach erosion mechanisms and implementation of effective protection schemes 3. Industrial processes. Development of improved models for solid phase transport in pipelines. Establishment of better models for removal (flushing) of solid phase contaminates.