Study of the lattice Boltzmann method applied to gas-liquid two-phase numerical simulations

Author(s)

Luiz Eduardo Czelusniak

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2022-06-03

Examining board members

Luben Cabezas Gómez; Alexys Bruno Alfonso; Leonardo Kleber Castelano; Jose Antonio Rabi; Carsten Alexander Johannes Heinrich Wolf Wagner

• Advisor: Luben Cabezas Gómez

Abstract

In this work a fundamental study of the pseudopotential lattice Boltzmann method (LBM-P) applied in two-phase gas-liquid simulations with and without phase change is carried out. The aim is to promote the development of the method and contribute to its future application in simulations of realistic boiling phenomena. In order to carry out this study, key points related to the method requiring further clarification in the literature are identified, such as: discretization forms, the role of state equations, and physical mechanisms related to phase change. A comprehensive study of MBR-P fundamentals and current applications is presented. Based on a theoretical analysis, discretization strategies of the method are discussed. Two approaches are developed, one based on the interaction force and the other on the pressure tensor. Several benchmarks tests are used to validate these approaches. It was found that the force approach is consistent for two-phase simulations while the pressure tensor approach showed some inconsistencies, still needing further studies. Subsequently, a study was presented on the role of the state equations in the accuracy and stability of the LBM-P. The effect of increasing the interface thickness was evaluated and a state equation modification procedure recently proposed in the literature was tested. It was found that the latter, drastically reduces the stability of the method in dynamic tests, despite increasing the accuracy. This motivated the development of a novel procedure able to present good results in thermodynamic consistency tests and high stability. Finally, the phase change mechanisms of the method were studied. For a simple two-phase system, with heat transfer from a heated surface to the liquid, it was possible to predict under which conditions the system boils and forms a new vapor phase. This process is directly linked to the state equation used in the model that determines which thermodynamic states are stable or unstable. It was also found that the magnitude of the gravitational field can affect the boiling temperature of the system due to changes in the pressure field. (AU)

• FAPESP's process: 18/09041-5 - Study of Lattice Boltzmann Method for modeling flows in microchannels of solar absorbers
• Grantee: Luiz Eduardo Czelusniak
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)