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Phase-­field modeling of multiphase flows using the lattice Boltzmann method with adaptive mesh refinement

Event Type: 
Date and Time: 
Friday, June 5, 2015 - 16:00
Location: 
CTR Conference Room 103
Event Sponsor: 
Parviz Moin, Director of Center for Turbulence Research
Speaker(s): 
Dr. Abbas Fakhari, CTR Postdoctoral Fellowship Candidate, Mechanical Engineering, City College of New York

Numerical modeling of multiphase flows at high Reynolds numbers is a challenging task. Traditional methods based on sharp-­interface models might encounter numerical difficulty in handling rapid topological changes such as breakup and coalescence. Therefore, diffuse-­interface models are widely used for numerical simulation of multiphase flows. As a diffuse-­interface model, the lattice Boltzmann method (LBM) is a well-­established mesoscopic scheme for numerical study of complex fluids. The most interesting feature of the LBM is that all nonlinearity is local and all nonlocality is linear, which is favorable for utilization on massively parallel machines. In this study, we increase the numerical stability of the LBM for multiphase flows at high Reynolds numbers, and investigate the Kelvin-­Helmholtz instability of a shear flow. In order to save the computational resources, we propose an efficient adaptive mesh refinement (AMR) algorithm which does not need to maintain or modify a tree data structure. We then reformulate the LBM on nonuniform grids and propose an AMR-­LBM for two-­phase flows. Various case studies such as rising bubble and falling drop under buoyancy force, drop splashing on a wet surface, and droplet coalescence onto a fluid bath are conducted for validation and verification. The Kelvin-Helmholtz instability of a stratified shear-­layer flow is also scrutinized to assess the accuracy of the proposed model, and satisfactory agreement with benchmark studies is shown.

Bio: 
Abbas Fakhari graduated with a Bachelor of Science in Physics from Zanjan University in 2006, and received his Master of Science in Mechanical Engineering from the University of Tehran in 2008. In 2010, he joined the Computational Multiphase Fluid Dynamics Group at the City College of New York, where he graduated with a PhD in Mechanical Engineering in 2015. His research interests include high-­Reynolds-­number multiphase flows, binary and ternary fluids, lattice Boltzmann methods, and adaptive mesh refinement techniques.