The ability to predict and understand particle entrainment and transport via the impelling force of moving fluid is important for engineering and natural applications including stream restoration and brownout conditions for helicopters. Most models predicting particle entrainment are empirically or semi-empirically based on temporally and/or spatially averaged velocity and/or shear stress of the fluid. As such, while these models work reasonably well for relatively simple fluid flow (through channels), under unsteady conditions (for example, due to existence of ripples in the bed or unsteady flow) these models are significantly less successful for flows heavily laden with particles. Further, even for statistically steady conditions, they fail to capture the physical essence of particle transport, adding to the prediction uncertainty. Experimental evidence suggests discrepancies in particle entrainment/transport models and physical measurements are due largely to the neglected effects of turbulence fluctuations on particle movement. A model relating locally-averaged turbulent fluctuations with locally-averaged particle transport could be of great value to parameterize particle entrainment, such as those available in large-eddy simulations. This research focuses on flow-driven particle transport where particle-particle interactions are important, specifically bedload transport in river channels. The central goal of this research is to better understand bedload transport from first principles. Ultimately, this might serve as a framework for particle entrainment in a wider range of flow-driven particle transport, such as wind-blown sand. The broader impacts involve the development of experiments and interactive online modules for middle-school, high-school and college students and related materials for K-12 teachers. These will be developed in particular for the National Center for Earth-surface Dynamics? (NCED) gidakiimanaaniwigamig (Our Earth Lodge) summer camps and after-school programming held at the Fond du Lac Tribal and Community College. Additionally, the PIs will incorporate the fundamentals behind the new model of particle transport into fluid mechanics and sediment transport courses they teach as well as the NCED post-baccalaureate Stream Restoration Certificate Program.
