Numerical Study on Diesel Oil Carrying Water Behaviors in Inclined Pipeline Based on Large Eddy Simulation

Tao Zhang,Zhao Zhang,Songqing Wen,Bin Chen,Xiaoqin Song

doi:10.1109/access.2019.2930757

Abstract

Water accumulation in low-lying areas of product oil pipelines always leads to corrosion damage of pipelines. Predicting the law of product oil carrying water can provide reference for the optimization of pipeline operation parameters and corrosion protection. A Volume of Fluid (VOF) model of oil-water two-phase flow based on Large Eddy Simulation (LES) was established to investigate the diesel oil carrying water behaviors in inclined uphill pipes. Through comparative study of experimental and simulation results based on Reynolds-Averaged Navier-Stokes (RANS) method, it is proved that the two-phase flow model based on LES-VOF can capture flow pattern characteristics such as wavy stratified flow, stratified flow and dispersed flow under different flow conditions. The model was used to simulate the oil carrying water process at different inlet oil flow velocities and inclination angles of uphill pipe on experimental scale. It was found that the shear rate of the oil-water interface increases with the increase of the inlet oil velocity, which leads to the increase of oil carrying water capacity. With the increase of slope angle, the two-phase flow pattern gradually transits from wavy stratified flow to dispersed flow. The model established in this paper provides a new method for the study of oil carrying water in product oil pipeline.

Highlights

In order to reduce the cost and shorten the production time, product oil pipelines are seldom carried out pigging and drying treatment after water transportation, resulting in water accumulation in the pipeline
Song et al [8] established an oil-water two-phase flow model based on Reynolds-Averaged Navier–Stokes (RANS) to study the effects of the superficial velocity of oil phase, inclination angle and initial water volume on flow characteristics
The results showed that non-stratified flow, such as bubble flow and slug flow, was the dominant flow pattern for upward flow, while stratified flow was the dominant flow pattern for downward flow

Summary

INTRODUCTION

In order to reduce the cost and shorten the production time, product oil pipelines are seldom carried out pigging and drying treatment after water transportation, resulting in water accumulation in the pipeline. When oil flow state is laminar flow, they analyzed the critical water phase thickness corresponding to the formation of water plug in oil-water system and the distribution of water phase thickness in flow direction Song et al [8] established an oil-water two-phase flow model based on RANS to study the effects of the superficial velocity of oil phase, inclination angle and initial water volume on flow characteristics. T. Zhang et al.: Numerical Study on Diesel Oil Carrying Water Behaviors in Inclined Pipeline Based on LES at different flow velocities, namely, Semi-Dispersed flow and Semi-Emulsion interface and Thin Oil film (SDSE&TO). According to the characteristics of oil carrying water behaviors in the uphill product oil pipeline, a VOF model of liquid-liquid two-phase flow based on LES is established and applied to verify the effectiveness of the model for oil-water two phase flow. Where, ui, uj are the velocities in the direction i and j respectively, m/s; p is pressure, Pa; ρ is the density of oil-water mixture, kg/m3; ν is the kinematic viscosity of the mixture, m2/s; Fs is the unit mass force obtained by surface tension conversion, m/s2; α is the volume fraction of the liquid phase, dimensionless

LES AND SUBGRID SCALE MODEL

INFLUENCE OF INCLINATION ANGLE