Simulation Of Flow Characteristics Of Gas-water Slug Flow In Horizontal Pipes

Two-phase flow widely exists in natural and industrial processes where slug flow is one of the most commonly encountered flow phenomenons. Because of the complex, unsteady and variant character of slug flow, the study of its flow characteristics and parameters measurement becomes a difficult and urgent issue in the field of engineering and science.Slug flow characteristics have been discussed by many researchers based on both experimental studies and the theoretical models, and great advances have been made. However, utilizing modern computational fluid dynamics technique to study slug flow has just come to a start. In light of the flow mechanism of two-phase flow, the characteristics of slug flow are studied through numerical simulation.The main achievements in this paper are as follows:1. Based on flow mechanism of two-phase flow, flow characteristics of gas-water slug flow were studied through computational fluid dynamics unsteady simulations. The formation of slug flow and the gas holdup, velocity, pressure as well as turbulent viscosity distribution are observed. The relationship between film velocity and slug velocity in a slug unit is obtained, and inter-slug structure is studied with the repeatability of slug fluctuations. The contributions to the pressure drop across a slug are also analyzed, and formulas are summed up to demonstrate such pressure drop.2. In order to further extract details of flow characteristics of slug flow and to investigate the flow condition and the numerical feature through the development of slug flow,"initial position"is proposed which analyzes the distributions of initial position under different conditions by statistical method. The results show that the pipe length has little effect on the initial position, and initial position increases with the increase of the pipe inner diameter and the inlet water velocity, and decreases with the increase of the inlet gas velocity.3. At the same distance from the initial position, the distribution of liquid slug length are observed with different inlet velocity, which shows the liquid slug length increases with the increase of inlet gas velocity, and decreases with the increase of inlet water velocity. The distribution of liquid slug length along the pipe shows that the length of the horizontal pipe required to reach quasi-stable slug flow is at least 300 times of pipe inner diameters, the distribution of liquid slug length at any part of the pipe is in agreement with normal distribution, and the maximum length is about 2 times of the mean slug length.