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

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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.