عنوان مقاله [English]
As gas and liquid flow simultaneously in a duct or pipe, different flow regimes will be generated. One of these regimes is called the slug flow, which is a common occurrence in gas-liquid two-phase flow in ducts. In recent decades, research into slug flow has increased because of gas and liquid transport, especially for applications with undersea reservoir operations with long pipelines. Information about the flow regime is necessary for thermal and hydraulic calculations. As pioneers declared, one of the most important considerations in the development of slug flow models is to predict slug frequency that has not been solved completely. This subject is a major issue that remains unsolved for two-phase flow in pipes or ducts.Many studies have reported results that are restricted to their experimental conditions, because different parameters can influence slug frequency. The numerical modeling of slug flow is important for simulation and prediction of physical behavior in gas-liquid transfer pipelines design, process equipment and, also, slug catchers.In this paper, air-water two-phase flow is simulated using the Pressure Free Model (PFM). The conservation equations are solved numerically by a class of high order shock capturing methods. To verify the various numerical methods in the developed code (Lax- Friedrichs, Ritchmyer, FORCE and FLIC), the water faucet problem is used. Comparison of the results with analytical solution of the benchmark cases shows good agreement. As the results of the developed codes verified, the FLIC method is selected to simulate the stratified air-water flow in a long horizontal channel. The results show good agreement in comparison with experimental data, which was conducted in the Multiphase Flow Laboratory of TMU. In this research, for the first time, it was found that the PFM under a well-posed condition could predict and evaluate two-phase flow behavior in long horizontal channels, in addition to slug frequency calculation and capturing the hydraulic jump, which forms before slug initiation.