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

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

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.