Liquid Sloshing Suppression for Three-Phase Separators Installed on Floating Production Unit

Abstract

In this study, a computational fluid dynamics model based on the volume of fluid (VOF) method is developed to simulate the dynamic sloshing response to external excitations. The modal analysis model based on the linear potential theory is established to predict natural sloshing frequencies and the corresponding mode shapes in three-phase separators. In addition, the effects of separator location, length-to-diameter ratio, oil/water level, porosity, and spacing of perforated baffles on the sloshing response are evaluated quantitatively. Furthermore, comprehensive approaches are proposed to mitigate the sloshing, like enhancing viscous damping effect, reducing the intensity of external excitation sources, and keeping away from the resonant frequencies. Finally, a practical application is carried out to display the optimal design of a three-phase separator. The results show that three-phase separators should be located as close as possible to the center of rotation (COR) of the floating production units (FPU). The length-to-diameter ratio is recommended to be no greater than three. Once the fluids can be separated to reach their respective interfaces, the liquid level should be increased as high as possible, whereas the water level should be lowered as far as possible. There is an almost inversely linear relationship between the antisloshing performance of a perforated baffle and its porosity. The antisloshing performance is attenuated rapidly when the spacing distance of a pair of baffles exceeds a specific range. This research extends the existing scope of sloshing suppression approaches and provides useful guidance in the design of FPU-based three-phase separators.