Keywords

lattice, Boltzmann, bubble, multiphase

Abstract

In recent years, the lattice Boltzmann method (LBM) has emerged as a powerful tool that has replaced conventional macroscopic techniques like Computational Fluid Dynamics (CFD) in many applications. The LBM starts from meso- and microscopic Boltzmann's kinetic equation to determine macroscopic fluid dynamics. The origins of LBM can be drawn back to lattice gas cellular automata (LGCA); however it lacks Galilean invariance and creates statistical noise in the system. LBM on the other hand does away from these drawbacks of LGCA, and is easy to implement in complex geometries and can be used to study microscopic flow behavior in complex fluids/fluid mixtures. In this work, the LBM is used as a tool to study isothermal bubble dynamics of single and multiple bubbles in heavier fluids. Some benchmark problems have been solved to prove the effectiveness of LBM over conventional solvers and results have been compared to analytical/existing solutions. Flow behavior at different flow parameters have been recorded and presented. Bubble shape regimes have been classified based on the important two-phase flow parameters, namely the Eotvos number, Morton number, Reynolds number and the Weber number. Single bubble simulations have been conducted in fairly large domains to capture terminal velocities, which have been compared to existing theoretical solutions, obtained using the potential flow theory. The terminal velocities so obtained have also been used for the estimation of drag and drag coefficient for a range of Eotvos and Reynolds numbers, and the drag coefficient so computed has been compared with those predicted by existing correlations and analytical expressions. Bubble dynamics and collision and coalescence for multiple bubbles rising under the influence of gravity in fully periodic domains have been simulated using LBM, and the flow behavior around such bubbles prior to and after coalescence have been studied and the results presented. The study of multiple bubble dynamics reveals the influence of the wake on the shape and collision of downstream bubbles, and yields valuable insights into the physics of intermediate stages when multiple bubbles collide and form an elongated/stretched bubble. The flow and bubble coalescence behavior predicted in this study compares very well with experimentally captured bubble dynamics and with data present in literature. Possible extensions of the present study have been highlighted for future research.

Notes

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Graduation Date

2007

Semester

Summer

Advisor

Kumar, Ranganathan

Degree

Master of Science in Mechanical Engineering (M.S.M.E.)

College

College of Engineering and Computer Science

Department

Mechanical, Materials and Aerospace Engineering

Degree Program

Mechanical Engineering

Format

application/pdf

Identifier

CFE0001728

URL

http://purl.fcla.edu/fcla/etd/CFE0001728

Language

English

Release Date

July 2008

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

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