Intrusion dynamics of particles or droplets released continuously to the deep ocean

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019Cataloged from PDF version of thesis.Includes bibliographical references.This thesis analyzes the flow and transport of multiphase plumes that result from a dispersed phase (e.g., droplets or particles) being discharged continuously into a stratified flowing ambient. Results are relevant to a wide range of natural and man-made applications, including the transport of oil droplets created accidentally during a deep-sea oil spill and sediment released purposefully during deep-sea mining operations. The subsequent transport and fate of small oil droplets with and without treatment using chemical dispersants is addressed experimentally and analytically. Next, we characterize the dependence of plume trapping behavior with crossflow velocity, bridging a gap in the current plume parametrization scheme. We also present a novel laboratory study aimed at understanding and quantitatively predicting secondary intrusion formation. In addition, a sensitivity analysis is conducted on plume trapping behavior to variations in key factors observed in the 2010 Deepwater Horizon oil spill field data. Another important environmental application of the study is deep-sea mining. Part of the work includes a field investigation to elucidate the trapping and dilution of mid-water plume consisted of fine sediment residuals from the mining operations, with the goal of assessing the potential environmental impact of this type of tailing disposal technique. Analytical and numerical model results are validated against field observations of the plume dynamics. Knowledge in this area helps the regulatory authorities to develop sound policies to better guide the mining activities in the deep sea to ensure sustainability of the resources and the environment.by Dayang Wang.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Civil and Environmental Engineerin