Two-phase slug flow is present in many industrial processes, such as the exploitation and transportation of hydrocarbon mixtures from oil wells. This kind of flow is characterized by two distinct structures which repeat intermittently: a liquid slug with a large amount of momentum followed by a compressible gas bubble. In recent decades, a few models for simulating such complex flows were developed, as the eulerian two-fluid model and drift flux, and the lagrangian slug tracking. The aim of this work is to present a detailed study on the numerical implementation of the hybrid model proposed by Fabien Renault and Nydal which is able to track down waves that arise in the gas-liquid interface and possible slugs generated by them. This model was developed from the two-fluid model equations in which the motion generated by the dynamic pressure of the gas on the slugs is decoupled from the slow movement of the liquid below the gas. The movement of the bubbles in the liquid is then modeled similarly to shallow-water equations. The solution of the equation set is achieved in two steps. The first step provides the pressure field and the gas flow through the numerical solution of the equations for the gas, using the finite difference method. The second step solves the adapted shallow-water equations analytically. The model was coded in object-oriented Intel Visual Fortran95. Simulations to analyze the ability of the code to generate slugs for some pairs of water-air superficial velocities at atmospheric pressure were carried out. The results, as the distribution of the slug length, frequency and average values were compared to experimental results reported in the literature.
Two phase flow occurs in many industrial applications, mainly in the transport of mixtures. Many patterns can be produced according to the liquid and gas flow rates. The identification of these patterns is very important in the design of piping systems and equipments. This work proposes an experimental study to identify multiphase flow patterns of water and air in horizontal pipes. The study was developed using an experimental circuit of 26 mm diameter and 9.2 m length pipe, at Thermal Sciences Lab (LACIT) at the Federal University of Technology - Parana´. To characterize the flow patterns, an intrusive mesh electrodes sensor was used, which allows the detailed visualization of the phases distribution. Tests were made using several experimental settings of water and gas flow rates. Measurements were compared to images obtained by high speed camera and the temporal void fraction series which were analyzed with the use of PDF and PSD functions, showing the singularities for each two-phase flow pattern.
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