Off-campus WSU users: To download campus access dissertations, please use the following link to log into our proxy server with your WSU access ID and password, then click the "Off-campus Download" button below.

Non-WSU users: Please talk to your librarian about requesting this dissertation through interlibrary loan.

Access Type

WSU Access

Date of Award

January 2022

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Mechanical Engineering

First Advisor

Leela Arava

Second Advisor

Hassan Farhat

Abstract

The intent of this work is to develop a 2D and 3D hybrid lattice Boltzmann color-gradient model to describe complex problems associated with surfactant-covered droplet behaviors in parabolic flows.The hybrid lattice Boltzmann color-gradient model coupled with surfactant and temperature dependent interfacial tension modules is improved upon by the addition of a robust contact angle module to investigate the combined multi-physics effects on oil-in-water (O/W) systems. The lack of experimental studies provides the need for such a model that includes all factors impacting the complexity of surfactant systems, including contact angle variance, surfactant type and concentration, thermal influence, surface energy, and droplet geometry. The focus is placed on the collective influence of all the parameters which impact the flow characteristics of O/W systems under Poiseuille flow conditions. The model investigates the optimal conditions required to improve the suspended phase transportation through droplet breakup at varying fluid temperatures. The results of the simulation demonstrate that the addition of surfactants, due to the increased contact angle and the deformation of the droplet influenced by specific surfactant distribution, markedly augments the suspended phase’s transportation inside the channel. An increase in the power number and an improvement in the suspended fluid transportation can be achieved by adding surfactants at specific conditions. A higher power number is associated with a reduction in consumed pumping power and an increase amount of useful work absorbed by the droplets. Moreover, a hybrid lattice Boltzmann model paired with temperature dependent interfacial tension, surfactant, and contact angle modules is extended to a 3D model. The latter model is employed in studying O/W flow characteristics passing through microchannels that contain confinements of varying heights, wherein the suspended phase is comprised of droplets and/or plugs. It is demonstrated that O/W emulsions with plugs as the suspended phase produce higher efficiency. Within mixed systems, those that have both droplets and plugs, conditions that lead to the droplets and plugs coalescing into larger plugs are more favorable. It is shown that confinement protrusions into the domain cause a hindrance to the system. Essentially, increasing the surfactant concentration and fluid temperate is the most feasible way to improve the system transportation efficiency. Finally, the developed 3D model is applied to examine the oil-water separation process in stable emulsions and to assess the efficiency of the superoleophilic/superhydrophobic filtration systems. The primary advantage to this LBM model is that it can represent the superwetting filter system using any desired contact angle and can assess the oil-water separation phenomena under a broad range of conditions and parameters. The following parameters are used to analyze the efficiency of the superwetting filtration system: droplet size, volume fraction, and suspended phase special distribution. The simulation results indicate that the superoleophilic-superhydrophobic filter type is an appropriate method for oil-water separation in stable emulsions as demonstrated by the high efficiency. Improvements can be made to the oil-water separation performance of superoleophilic/superhydrophobic filters by increasing the dimensionless droplet radius and volume fraction.

Download
Off-campus Download

Share

COinS