CFD investigation of core annular flow effect on total pressure drop of the crude oil transportation at different inclination angles

In this study, a three-dimensional numerical simulation has been developed using computational fluid dynamics (CFD) utilizing the volume of fluid (VOF) method to examine the real-scale, 20 mm diameter, with 20 m long crude oil-water core-annular flow for a crude oil transportation pipeline with different orientations (0o, +15o, +30o, +45o, +60o, +75o and +90o). The core-flow technique reduces friction during heavy oil transportation by altering the flow pattern rather than the oil's viscosity. A fine water film forms on the inner surface of the pipe and acts as a lubricant for the oil flowing in the core of the pipe. This is the specificity of this flow pattern. Furthermore, the simulation showed that there was acceptable agreement between the experimental results found in the literature and the CFD analysis. It was found that the water film flowing in the pipeline around the heavy oil core significantly lowers the pressure loss in the crude oil conveyance pipeline, which in turn lowers the pumping power consumption by about 50% in horizontal and about 59% in vertical inclination angles. The findings showed that at the beginning of the flow, a water film forms close to the pipe wall; however, this annular layout does not last to the end and disappears at 4 meters from the pipe intake in horizontal orientation. Additionally, in a vertical orientation and at the start of the flow, a water film developed close to the pipe wall, and this annular pattern persisted until the end of the pipe.