The transportation of high viscous oil surrounded by a water layer is one of the energy efficient technologies. In this study, the VOF, standard k-epsilon, and CSS models are performed to simulate the oil water core annular flow across a Pi bend, and the tendency of phase contour and phase fraction simulated appears reasonably consistent with the photo from experiments and the empirical correlation. The effects of input water fraction, the flow direction, the oil property, and the geometric parameters (include aspect ratio, diameter ratio, fillet radius, and roughness) on hydrodynamic performance and fouling characteristics are analyzed, and the results could provide a reference for designing the pipeline and optimizing operation conditions and the Pi bend structures.