Modelagem matemática e computacional de escoamentos turbulentos multifásicos em malha adaptativa bloco estruturada utilizando o método multi direct forcing

Abstract

Flows in horizontal pipes where a liquid phase and a gas phase coexist are common in many fields of the industry. The distribution of phases can take different forms, known as flow patterns. The characterization of these flows can help to predict, for example, erosion and corrosion rates, in addition to pressure fluctuations over time and in the duct, which can cause vibrations or mechanical deformations. The objective of the present work is to analyze, through computer simulations, the transition between the stratified flow and slug flow patterns in horizontal pipes. The numerical platform used is an adaptive structured block mesh code developed at the Fluid Mechanics Laboratory of the Federal University of Uberlândia, called MFSim. Due to the characteristics of the physical problem addressed and the numerical platform used, throughout the work, modeling related to turbulent flows, multi-phase flows, and treatments for the representation of immersed bodies in structured meshes, the so-called immersed boundary methods, were developed, and tested. Among the developments, it is worth highlighting a multi-direct forcing method for k and epsilon used in simulations with turbulence models of the k-epsilon class. Are presented tests of several functionalities involved in the immersed boundary method and in the methodology for treating two-phase flows used, the Volume of Fluid (VOF). At the end are presented the results and analysis of computer simulations of the transition between the stratified and slug patterns in horizontal pipes with rectangular and circular sections. The results and reference values from the literature obtained with experiments and computer simulations were compared. It was observed that, compared with other codes, the MFSim performance in the prediction of parameters such as time and location of first slug formation and average holdup was above that obtained through other codes. In summary, the method implemented and the developments in this work represent an expressive advance involving the MFSim platform for the simulation of a new problem that includes a series of complex physical mechanisms.