Multi-scale studies on the effects of fluid and bed variability on particle entrainment and transport

CBET-0756480Hill 通过移动流体的推动力来预测和理解颗粒夹带和传输的能力对于工程和自然应用（包括河流恢复和直升机的停电条件）非常重要。大多数预测颗粒夹带的模型都是基于流体的时间和/或空间平均速度和/或剪切应力凭经验或半经验进行的。因此，虽然这些模型对于相对简单的流体流动（通过通道）效果相当好，但在不稳定条件下（例如，由于床中存在波纹或不稳定流动），这些模型对于充满颗粒的流动明显不太成功。此外，即使在统计稳定的条件下，它们也无法捕捉粒子输运的物理本质，从而增加了预测的不确定性。实验证据表明，颗粒夹带/传输模型和物理测量的差异很大程度上是由于忽略了湍流波动对颗粒运动的影响。将局部平均湍流波动与局部平均粒子输运相关的模型对于参数化粒子夹带具有很大价值，例如大涡模拟中可用的模型。这项研究的重点是流动驱动的颗粒输送，其中颗粒与颗粒的相互作用很重要，特别是河道中的床质输送。这项研究的中心目标是从第一原理更好地理解垫料输送。最终，这可能作为更广泛的流动驱动颗粒传输（例如风吹沙子）中颗粒夹带的框架。更广泛的影响包括为初中生、高中生和大学生开发实验和交互式在线模块，以及为 K-12 教师开发相关材料。这些将是专门为国家地球表面动力学中心开发的？ (NCED) gidakiimanaaniwigamig（我们的地球小屋）夏令营和课后活动在 Fond du Lac 部落和社区学院举办。此外，PI 还将把新粒子传输模型背后的基础知识纳入他们教授的流体力学和沉积物传输课程以及 NCED 学士学位后河流恢复证书课程中。

CBET-0756480HillThe 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.