RAPID: Sub-Mesoscale Dynamics of Buoyant Plumes

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Intellectual Merit: This RAPID response research project addresses several important scientific issues associated with the massive ongoing Deepwater Horizon oil spill that started to release large amounts of oil (more than 5,000 barrels/day) from a depth of 1,500 m on April 20, 2010. The main objective of the project is to explore the behavior of buoyant plumes released from a point source at the bottom of a stratified and rotating oceanic environment through large eddy simulations, as a step towards resolved modeling of oil and gas plumes in the future. In particular, the following questions will be addressed:(i) What are the flow patterns of buoyant plumes in the presence of sub-mesoscale (spatial range of 100 m to 10 km, temporal range of few days to few weeks) oceanic environment? Does it show subsurface intrusions detraining from the main plume? How does the buoyant plume interact with mixed layer density fronts? What are the parameters controlling the plume?s ability to reach the surface? How much of the total discharge is expressed at the surface? (ii) What is the three-dimensional relative dispersion of the plume. How do surface and subsurface relative dispersion differ?(iii) What is the nature of dispersion of a three-dimensional buoyant plume after its source is shut down? How long does it take to dissipate? Where does it modify the surrounding water characteristics?While this study will be conducted mainly within the context of a Boussinesq, Newtonian fluid model, two simple modifications will be considered. The first is the addition of evaporation to represent loss of volume over the first two days after surfacing, and the second one is the inclusion of non-Boussinesq effects in order to include density differences between oil and water of some 20%. The computations will be carried out employing the spectral element code Nek5000 in collaboration with Paul Fischer and Aleks Obabko on Argonne National Laboratory.?s IBM BL/G Intrepid machine on up to 32,000 CPUs. Broader Impacts: Broader impacts of the project include a strengthening of the ongoing collaboration between scientists from the University of Miami, Argonne National Laboratory and the Naval Research Laboratory at Stennis Space Center to make progress in different aspects of the problem in preparation for future events. The results from this study may also lead to better sampling techniques of buoyant plumes and provide guidance on how to initialize larger scale ocean circulation models. It is also a good step for future development of advanced two-phase computational models for oil spill applications.