Three Phase Flow Simulations of an Oil Recovery Ship in Various Sea States

The analysis of local flow phenomena, in particular the analysis of the oil flow and the oil-water separation process in a three phase flow simulation (air, water, oil), including the free water surface, is a basic need for the development of an efficient oil recovery system such as the Seaway Independent Oilskimming System (SOS). As the oil separation process is highly dependent on the ships motions, its seakeeping behaviour needs to be simulated accurately. The paper presents two-phase flow simulations (air, water) of the seakeeping behaviour in three and six degrees of freedom (two- and three-dimensional — 2D/3D). The vessel motions simulated in various sea states are validated by model tests conducted in a physical wave tank. The grid resolution as well as the flow parameters of the simulation have been varied to find a fast and reliable solution. The need for three dimensional simulation runs is questioned, as two dimensional simulations give nearly the same results and are far less time intensive. Oil is introduced as the third phase. The associated analysis illustrates the oil-water separation process and yields the systems efficiency in dependency of the sea state conditions. Based on the results of three-phase simulations, the operational range of the Seaway Independent Oilskimmer is determined and recommendations for the system optimization can be made.