A TWO-FLUID MODEL FOR SLUG CAPTURE USING A LAGRANGIAN SCHEME
Marco Germano Conte1; Melissa Bianca Mendes1; Fausto Arinos Barbuto2; Rigoberto Eleazar Melgarejo Morales2
1 NUEM - UTFPR; 2 UTFPR
doi:10.20906/CPS/CILAMCE2015-0664
Resumo
Two-phase slug flow in pipes occurs frequently in the petroleum and nuclear industries. By and large, slug flow differs from the other two-phase flow patterns due to its complexity. Slug flows are characterized by intermittent liquid slugs that fill the whole cross section of a pipe, followed by gas pockets called elongated gas bubbles. 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 influence of the integration parameters (i.e. mesh size and time step) were analyzed and a criterion for the minimum grid length in order to maximize the number of slugs in the simulations for a given time step was proposed. The results, as the distribution of the slug length, bubble length, unit-cell frequency and mean slug frequency were compared to experimental data acquired at the NUEM/UTFPR labs to support slug initiation studies.
Palavras-chave: Two-phase slug flow; Slug capturing; Slug initiation