Hydrodynamic Simulation and Optimization of an Oil Skimmer

Oil spills can cause severe environmental damage. In-situ burning or chemical dispersant methods can be used in many situations; however these methods are highly toxic and fail in slightly rough seas. In-situ burning also has to begin very quickly before the lighter, flammable components in the oil evaporate. Oil recovery techniques have also been developed to recover oil using skimmer equipment installed in ships. The challenges arise when a vessel is operated in heavy sea and current conditions. An oil skimmer has recently been developed by the Extreme Spill Technology (EST) Inc. for automated oil recovery using a vacuum device installed in a vessel. Initial tests have shown that the prototype vessel is efficient in oil recovery and it can potentially achieve high recovery efficiency in rough seas of both deepwater and shallow water. The paper presents the numerical and experimental studies of the hydrodynamic performance of the vacuum tower installed in the oil skimmer developed by EST. The process of oil recovery by the vacuum mechanism is very complicated and involves multi-phase and multi-scale moving interfaces, including oil, water, atmospheric air and attenuate compressible air on the top part of the vacuum tower, and moving interface of oil slick, oil droplets and air bubbles of different scales. The recovery process was simplified into a three-phase flow problem involving oil, water and air and simulated by using a CFD method. The volume of fluid (VOF) method was employed to capture the moving surfaces between the fluid phases. Model tests were carried out to simulate the oil recovery process. Numerical results were compared with the experimental data. Studies were also extended to optimize the geometry of the tower for maximum oil recovery.