In the aftermaths of deep water blowouts, oil plumes rise through and interact with various layers of the ocean and arrive in the upper ocean. There, several physical dispersion mechanisms such as turbulence, Langmuir circulations and sub-mesoscale eddies affect their evolution. Numerical modeling of these processes is playing an increasingly important role for estimating total oil spill volume and rate of biodegradation, planning for dispersant injection, and predictions/postdictions in general.
Existing mesoscale ocean transport models neglect processes that have been shown to be crucial in determining the transport direction, shape, and the overall size of oil plumes. Oil plumes consisting mostly of large droplets that stay predominantly at the surface move faster and in a different direction from plumes of mostly small droplets that are vertically better mixed within the ocean mixed layer subjected to Langmuir circulations. Chemical dispersants are known to strongly affect droplet diameter, drastically reducing it. Thus, dispersants may be used not only to affect the plume composition and susceptibility to be biodegraded, but also its transport direction, size and surface signature.
To better quantify and understand such effects, a high-fidelity multiscale simulation framework must be developed that covers the relevant length and time scales and particular needs of modeling polydisperse oil droplet dispersion in the ocean. In this project we will develop and apply an enhanced Large Eddy Simulation (LES) framework for prediction of multiscale physical dispersion mechanisms and effectiveness of remediation strategies.
The proposed research activities have four main goals: (i) develop a transport model for evolution of entire distributions of oil droplet sizes in LES and effects of dispersants on the size distribution. To address this goal, a multi-species LES framework will be developed to model droplet population dynamics (droplets of various sizes), and their interactions with surfactants. Another goal is to (ii) develop the Extended Nonperiodic Domain LES for Scalar Transport (ENDLESS) methodology that enables simulating plumes extending over physical scales that greatly exceed the size of the computational LES domain and thus couples the transport with outputs from larger (meso or sub-meso) scale regional ocean models. The ENDLESS method will be validated by comparing with CARTHE Lagrangian drifter data that covers many orders of magnitude of relevant length and time scales. (iii) By means of a series of simulations, explore effects of dispersants on plume evolution for both underwater and surface application of oil dispersants, with various overall dosage, release rates and locations, under various wind and wave conditions. (iv) Results will be used to develop engineering tools for rapid real-time assessment and parameterizations for regional scale ocean models.
This 3-year project addresses GoMRI's Research Theme No. 1, dealing with physical distribution, dispersion, and dilution of petroleum under the action of physical oceanographic processes and air-sea interactions. By applying state-of-the-art enhanced LES tools to the field of oil-spill modeling, fundamental new insights will be developed in a research area with direct applications to the challenges confronting the Gulf of Mexico region and the energy industry.
Project Research Overview (2016):
An overview of the proposed research activities from the GoMRI 2016 Meeting in Tampa.
Direct link to the Research Overview presentation.