Numerical Modeling of Oil Containment
by a Boom
Project summary :
A two-dimensional model of oil containment by a boom has been developed at the University of Rhode Island (URI) as part of a research effort funded by the U.S. Coast Guard (Phase I and II). This model is now being extended and improved to address more realistic problems, as part of Phase III, under funding of U.S. Mineral Management Service (MMS).
Model results will be compared/calibrated with experimental data obtained at the University of Hew Hampshire (UNH), as part of a parallel research effort, and with results from MMS's OHMSETT facility. These comparisons will be restricted to uniform flow cases without waves. The use of instability delaying techniques (structural, chemical) will then be investigated. Finally, the effects of surface waves on oil-containment failure will be investigated; these will be included in the model and results compared to experimental data.
This project is part of an ongoing research project funded by the U.S. Coast Guard (USCG) at the University of Rhode Island (URI), during FY94 and FY95 of the ``Oil Pollution Research Grant Program'' : Numerical Modeling Of Oil Containment By a Boom/barrier System (Phase I and II), and by the U.S. Mineral Management Service (MMS) during FY96,97,98 (Phases III and III/2).
The FY94 project was aimed at developing a two-dimensional hydrodynamic model of oil containment---mostly by booms---to be used to investigate oil containment failure identified and studied over the past 25 years (Figs. 1 and 2). It was envisioned that this numerical model and its future improvements would help us both gain fundamental insight into oil containment failure mechanisms and outline strategies and methods to limit the occurrence or the intensity of these failures in actual field situations. Due to its more catastrophic nature, the failure mode referred to as critical accumulation was to be the main object of the study. Three main technical tasks were initially proposed : (i) numerical model selection and design; (ii) model testing and validation; and (iii) application to oil containment failure. Extensive literature review and analysis of the physical, theoretical, and numerical problems relative to oil containment were conducted as part of task (i) (Grilli et al. 1996a). Based on this review, an initial modeling strategy was selected (hereafter referred to as the Phase I model). The Phase I model was implemented and validated, and applied to predict oil containment failure, as part of tasks (ii) and (iii). In all cases, model results showed the expected failure modes and the correct sensitivity to changes in physical parameters. Details of the Phase I model development, implementation, and results can be found in Grilli et al. 1996ab.
The FY95 project involved various improvements of the Phase I model, hereafter referred to as the Phase II model, at the level of both the modeled physics (e.g., inclusion of viscous/turbulent effects at the oil-water interface) and of the numerical methods used (e.g., higher-order discretization and time updating techniques). Using the Phase II model, a partial parametric study of critical accumulation failure was conducted at the end of the FY95 project, where values of important parameters such as oil density, viscosity and surface tension, and oil-water velocity, will be varied. Based on results of this parametric study, additional computations will be carried out in order to determine parameter values for which critical accumulation failure might be delayed (i.e., increased to higher speed). Design of boom/barrier systems can thus be optimized, within given specifications.
Despite their accuracy and relevance, the main drawbacks of the numerical models developed so far is that there has been no comparison (and calibration) with experimental results and that the models have assumed no surface waves. Over the past two years, however, an experimental research effort was funded under the same USCG program, at the University of New Hampshire (UNH), to develop fast current oil barriers. As part of this study, various experiments were conducted in a two-dimensional flume with recirculation to study instabilities of contained oil slicks and to develop methods for limiting the loss of oil (e.g., submergence plane concept). The UNH flume is thus well-suited to conduct idealized, well-controlled, two-dimensional laboratory experiments, using real oil, that could be exactly simulated in URI's numerical model. Numerical and experimental results were cross-validated during FY96 and FY97 and the numerical model was calibrated based on experiments. This was done as part of Phase III of this project.
Finally, numerous large scale three-dimensional experiments, with towed booms, werre conducted over the past several years, at MMS's OHMSETT flume in New Jersey. Results of past and similar future experiments can provide valuable information on three-dimensional effects neglected in the numerical model and in UNH's experimental facility. In addition, the OHMSETT facility is equipped with a wavemaker and can thus provide information on surface wave effects. This was initiated during Phase III of this project. During the ongoing Phase III/2, additional experiments will be performed at OHMSETT and the models will be further calibrated. The models will then be implemented into a user friendly interactive interface, and distributed to potential users.
Funding history :
Key personnel at URI :
Back to top of page
Back to Ocean Engineering Home Page