The Role of Fluctuating Fluid Forces on the Initiation of Sediment Motion

该项目的目标是确定在波动水动力影响下（通常在湍流中遇到）泥沙移动的关键参数。提出了在接近阈值条件下检验力-时程（脉冲）和惯性力对粒子夹带的作用的实验。实验将在现有的研究水槽中进行，在水槽中，将使用定制设计和制造（磁性）的球形测试颗粒测量孤立球形颗粒的力，以便测量有限的完全时间分辨的表面压力。通过无运动、稳定均匀湍流运动和空间加速湍流运动实验，探讨粘性阻力、惯性和冲量对泥沙夹带的影响。在实验期间，将使用数字视频摄影和声学多普勒传感器（用于水力测试）来监测目标粒子的运动，如最近的试点测试所示。制定更普遍的运动条件阈值标准将改善现有的稳定水道设计工程方法，并建立更好的基于风险的方法来防止污染沉积物的清除。

The goal of this project is to determine the key parameters responsible for sediment dislodgement under the influence of fluctuating hydrodynamic forces, typically encountered in turbulent flows. Experiments are proposed to examine the role of force-time history (impulse) and inertia forces on particle entrainment at near threshold conditions. The experiments will be performed in an existing research flume, where the forces on an isolated spherical particle will be measured using an instrumented spherical test grain custom designed and fabricated (magnetic) such that a limited set of fully time-resolved surface pressures can be measured. The effects of viscous drag, inertia, and impulse on sediment entrainment will be explored through experiments including no motion, steady uniform turbulent motion and spatially accelerating turbulent motion. During the experiments digital video photography and acoustic Doppler sensors (for the hydraulic tests) will be used to monitor the target particle movement as demonstrated in recent pilot tests. Developing more universal criteria for threshold of motion conditions will improve existing engineering methods for the design of stable waterways and establish better risk-based methods for preventing the removal of contaminated sediments.