The subsurface plume from the Deepwater Horizon (DH) accidental oil-well blowout is a complex, layered system of intrusions containing oil, dissolved hydrocarbons, and injected dispersants that will have far-reaching environmental consequences; however, no modeling tools are currently producing highly-resolved predictions of the plume structure and evolution. The goal of this Rapid Response Research Proposal (RAPID) is to develop a three-dimensional, multiscale hydrodynamic model for the DH blowout plume that combines the Reynolds averaged Navier Stokes (RANS) modeling approach with the method of large-eddy simulation (LES). The resulting model platform will be validated to field and laboratory data, will respect the relevant chemistry and thermodynamics of the released oil and natural gas, and will be forced by the measured ambient conditions surrounding the spill. Such a simulation tool is urgently needed to guide field observations, predict the onshore migration and loop-current capture of the spilled oil, assess the effectiveness and potential environment impact of dispersants injected at the source, and to understand the response to this event already measured in the vertical migration of plankton and fish. The validated modeling platform will be developed through complementary laboratory experiments, numerical modeling, and analysis of field data. The laboratory experiments will evaluate the effects of currents as the flow through the plume and pull oil and dissolved constituents into the wake of the plume. The numerical methods will utilize a very large eddy simulation (VLES) to resolve the dominant plume structures in the near field of the blowout plume and will nest this model in a far-field model based on the unsteady RANS approach. Field data from acoustic Doppler current profilers will provide model forcing and validation data and will also be analyzed to understand the role of subsurface plume dynamics on the vertical migration of plankton and fish as also recorded in the ADCP data. Early analysis of this data shows a very rapid shut-down of the diurnal vertical migration pattern at nearby stations shortly after the start of the spill. This is the first documented environmental response to the blowout, and it remains unknown whether this is due to mortality, avoidance, light penetration changes or other processes. The sub-surface plume model developed here will provide detailed predictions of the subsurface plume structure necessary to analyze this environmental response.
Intellectual Merit: The primary intellectual merit of the project will be an understanding of the critical physical and chemical processes in an accidental oil-well blowout that lead to the subsurface layered structure of oil and dissolved hydrocarbons in the water column. Important insight will also be gained on the appropriateness of a classical RANS model for predicting the dynamics of the oil and gas intrusions. Broader Impact: Predictions from the model will help guide the collection of observation data in the field and will be applied to understand why plankton and fish in the vicinity of the blowout shut down their vertical migration pattern shortly after the blowout. The model is also needed to predict the transport of oil and injected dispersants throughout the Gulf ecosystem, including onshore and into the loop current and potentially into the Atlantic ocean. Detailed studies of turbulence in multiphase plumes conducted in the later stages of the project will ultimately result in a reliable model framework featuring a zonal RANS-VLES simulation tool applicable to a wide range of environmental applications of multiphase plumes, including CO2 sequestration, lake aeration, and sediment plumes, among others.
