Collaborative Research: Advancing turbidity currents: moving sources, polydispersity and aggregation

重力流主要是由流体中的密度变化或两种流体之间的密度差异驱动的水平流动。它们在湖泊、河流和海洋中的沉积物运输中发挥着核心作用，在深海采矿和地球工程等新兴和潜在变革性技术中也发挥着重要作用。尽管对重力流的研究有着丰富的历史，但一些基本的情景还没有得到探索，或者仍然基本上没有解决。这个合作项目将把分析建模、数值模拟和实验室实验与一个独特的现场实验数据集结合起来，以促进对颗粒重力流的理解。该项目通过为深海采矿等新兴行业提供环境法规，有可能产生变革性的影响。深海采矿预计将使原始深海环境中的大量沉积物重新悬浮，通过该项目开发的知识和模型将提供评估这些沉积物羽流演变所需的工具箱。该项目将为所有学术水平的大学生和高中生提供培训，这些学生将通过麻省理工学院和UCSB的现有项目参与该项目。该项目分为三个相互关联的主题。第一个是关于重力和从移动的源释放的粒子驱动的电流的演变。其目标是了解源速度与浮力速度的比率如何影响海流的动力学，调查背景流的作用，并开发预测传输过程的经验模型。第二个重点是通过同时进行的实验室实验和数值模拟，量化多分散颗粒驱动的水流中的泥沙剥离，并确定其对颗粒大小和速度分布的敏感性。多分散粒子驱动流的经验模型将扩展到包括卷吸和脱吸，并纳入移动源重力流模型。最后，将通过系统地改变沉积物的历史来实验研究颗粒的絮凝和聚集在多分散颗粒驱动的水流传播中的作用，目的是开发用于絮凝的大尺度数值模型，并将结果整合到移动源模型中。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Gravity currents are mostly horizontal flows that are driven by density variations in a fluid or by density differences between two fluids. They play a central role in the transport of sediment in lakes, rivers, and oceans, and they are also important in emerging and potentially transformative technologies such as deep-sea mining and geoengineering. Despite a rich history of research on gravity currents, some fundamental scenarios have yet to be explored or remain substantially unresolved. This collaborative project will integrate analytical modeling, numerical simulation and laboratory experimentation with a unique field experimental data set to advance understanding of particle-laden gravity currents. This project has potential for transformative impacts by informing environmental regulations for such emerging industries as deep-sea mining. Deep-sea mining is expected to re-suspend large volumes of sediment in the pristine abyssal ocean environment, and the knowledge and models developed through this project will provide the toolbox needed to assess the evolution of these sediment plumes. The project will provide training for university students at all academic levels and for high-school students who will participate in the project through established programs at MIT and UCSB. The project is divided into three interconnected topics. The first concerns the evolution of gravity and particle-driven currents released from a moving source. The goals are to understand how the ratio of source speed to buoyancy velocity influences the dynamics of the current, investigate the role of background current, and develop empirical models that predict transport processes. The second point of focus is to quantify sediment detrainment from polydisperse particle-driven currents and determine its sensitivity to the particle size and velocity distribution through concurrent laboratory experiments and numerical simulations. Empirical models of polydisperse particle-driven currents will be extended to include entrainment and detrainment and incorporated into the moving source gravity current model. Finally, the role of flocculation and aggregation of particles on the propagation of polydisperse particle-driven currents will be experimentally investigated by systematically varying the sediment’s history, with the goal of developing macroscale numerical models for flocculation and integrating the findings into the moving source model.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.