Browsing by Author "Shi, Jing"
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Item Open Access CFD simulation of horizontal oil-water flow with matched density and medium viscosity ratio in different flow regimes(Elsevier, 2017-01-10) Shi, Jing; Gourma, Mustapha; Yeung, HoiSimulation of horizontal oil-water flow with matched density and medium viscosity ratio (μo/μw=18.8) in several different flow regimes (core annular flow, oil plugs/bubbles in water and dispersed flow) was performed with the CFD package FLUENT in this study. The volume of fluid (VOF) multiphase flow modeling method in conjunction with the SST k-ω scheme was applied to simulate the oil-water flow. The influences of the turbulence schemes and wall contact angles on the simulation results were investigated for a core annular flow (CAF) case. The SST k-ω turbulence scheme with turbulence damping at the interface gives better predictions than the standard k-ε and RNG k-ε models for the case under consideration. The flow regime of density-matched oil-water flow with medium viscosity ratio, or more generally speaking, the flow regime of fluids where the surface tension is playing a prevailing role is sensitive to the wall contact angle. Simulation results were compared with experimental counterparts. Satisfactory agreement in the prediction of flow patterns were obtained for CAF and oil plugs/bubbles in water. The simulation results also demonstrated some detailed flow characteristics of CAF with relatively low-viscosity oil (oil viscosity one order higher than the water viscosity in the present study compared to the extensively studied CAF with oil viscosity being two to three orders higher than the water viscosity). Different from the velocity profiles of high-viscosity oil CAF where there is sharp change in the velocity gradient at the phase interface with velocity across the oil core being roughly flat, there is no sharp change in the velocity gradient at the phase interface for CAF with relatively low-viscosity oil.Item Open Access Characterization of liquid-liquid flows in horizontal pipes(Wiley, 2016-08-26) Shi, Jing; Yeung, HoiDiverse flow regimes have been encountered in liquid-liquid flows. Some degree of consistency in the observed flow patterns is shown in reported studies, while inconsistency exits when physical properties of the two phases concerned are wide enough. An attempt was made in this study to investigate the mechanisms behind flow patterns of liquid-liquid flows in horizontal pipes. A literature review on flow patterns of liquid-liquid flows in horizontal pipes was conducted. The ratio of the gravitational force to viscous force was proposed to characterize liquid-liquid flows in horizontal pipes into gravitational force dominant, viscous force dominant and gravitational force and viscous force comparable flow featured with different basic flow regimes. Comparisons of the proposed characterization criterion with the literature data show good agreement.Item Open Access A study on high-viscosity oil-water two-phase flow in horizontal pipes(Cranfield University, 2015-09) Shi, Jing; Yeung, HoiA study on high-viscosity oil-water flow in horizontal pipes has been conducted applying experimental, mechanism analysis and empirical modelling, and CFD simulation approaches. A horizontal 1 inch flow loop was modified by adding a designed sampling section to achieve water holdup measurement. Experiments on high-viscosity oil-water flow were conducted. Apart from the data obtained in the present experiments, raw data from previous experiments conducted in the same research group was collated. From the experimental investigation, it is found that that the relationship between the water holdup of water-lubricated flow and input water volume fraction is closely related to the oil core concentricity and oil fouling on the pipe wall. The water holdup is higher than the input water volume fraction only when the oil core is about concentric. The pressure gradient of water-lubricated flow can be one to two orders of magnitude higher than that of single water flow. This increased frictional loss is closely related to oil fouling on the pipe wall. Mechanism analysis and empirical modelling of oil-water flow were conducted. The ratio of the gravitational force to viscous force was proposed to characterise liquid-liquid flows in horizontal pipes into gravitational force dominant, viscous force dominant and gravitational force and viscous force comparable flow featured with different basic flow regimes. For viscous force dominant flow, an empirical criterion on the formation of stable water-lubricated flow was proposed. Existing empirical and mechanistic models for the prediction of water holdup and/or pressure gradient were evaluated with the experimental data; the applicability of different models is demonstrated. Three-dimensional CFD modelling of oil-water flow was performed using the commercial CFD code Fluent. The phase configurations calculated from the CFD model show a fair agreement with those from experiments and mechanism analysis. The velocity distribution of core annular flow is characterised with nearly constant velocity across the oil core when the oil viscosity is significantly higher than the water viscosity, indicating that the high-viscosity oil core flows inside the water as a solid body. The velocity profile becomes similar to that of single phase flow as the oil viscosity becomes close to the water viscosity.Item Open Access Water-lubricated transport of high-viscosity oil in horizontal pipes: the water holdup and pressure gradient(Elsevier, 2017-07-05) Shi, Jing; Lao, Liyun; Yeung, HoiThis paper has investigated the water holdup and the pressure gradient of water-lubricated transport of high-viscosity oil flow in horizontal pipes. Experimental results on the water holdup and the pressure gradient of water-lubricated high-viscosity oil two-phase flow in a horizontal 1 in. pipe were discussed. Models for the prediction of the water holdup and/or the pressure gradient of core flow or water-lubricated flow were reviewed and evaluated. It was found that the water holdup of the water-lubricated flow is not only closely related to the input water volume fraction but also the degree of the oil phase eccentricity which is attributed to the oil phase Froude number. This can explain the inconsistency of the experimental results with regard to the relationship between the water holdup and the input water volume fraction in the literature. The applicability of the existing empirical or mechanistic models of water-lubricated high-viscosity oil flow were discussed and demonstrated. A modified correlation to the water holdup correlation of Arney et al. (1993) which was shown to be exclusively applicable for concentric core flow was introduced for stable water-lubricated flow, including both concentric and eccentric core flows. This correlation was evaluated and a fair applicability was shown. The accuracy of different models for the prediction of the pressure gradient of water-lubricated transport of high-viscosity oil was demonstrated to be not high in general. This is closely associated with the difficulty in accurately accounting for the influence of oil fouling on the pressure gradient.