Simulation of Ternary Fluid Systems in T-junction Microfluidics Devices with Lattice Boltzmann Method

Microfluidic systems have emerged as a transformative technology, enabling precise manipulation of fluids at the microscale with applications spanning drug delivery, chemical synthesis, and biomedical diagnostics. These systems rely on the controlled generation and manipulation of droplets, particularly in complex multiphase environments like ternary fluids, where three immiscible phases interact. Numerical simulation plays a critical role in advancing microfluidic research by providing a cost-effective and flexible means to study intricate fluid dynamics, optimize device design, and predict droplet behavior. This thesis focuses on the numerical simulation of droplet generation in ternary fluid systems, employing the Lattice Boltzmann Method (Cahn-Hilliard method) to model the complex interfacial dynamics. A significant effort was dedicated to developing and validating an LBM-based code, by use of literature benchmarks and analytical solutions to ensure accuracy. This thesis significantly advances the numerical simulation techniques for ternary fluid systems using the Lattice Boltzmann Method (LBM Cahn-Hilliard), providing a robust framework for modeling complex multiphase flows in intricate geometries. Key validations include: Static droplet simulations, confirming precise interfacial tension balance, critical for stable fluid interactions; Spinodal decomposition, important to accurate modeling of phase separation dynamics, essential for material design; Liquid lens formation, validating interfacial energy minimization, key for emulsion stability; Wettability modeling, enabling accurate fluid-solid interactions for microfluidic applications presenting hydrophilic and hydrophobic properties of the channel surface; Compound droplet dynamics under shear, capturing flow-driven behavior, vital for lab-on-chip systems; An Adapted and modified outlet boundary conditions (Convective Boundary Condition), with a novel application strategy ensuring realistic and smooth droplet exit in confined flows; Droplet morphology studies, linking interfacial properties to double emulsion formation for drug delivery; and Flow-focusing device simulations, reproducing jetting and dripping regimes with an 8.5% discrepancy from experiments, demonstrating practical applicability. By developing a novel computational framework, this thesis has successfully captured the satellite-like regime and Rayleigh-Plateau instability, having intricate dynamics, revealing previously unexplored behaviors and properties. This work establishes a reliable platform for simulating complex geometries of devices. These contributions enhance the understanding of multiphase dynamics and lay a foundation for innovations in drug delivery, polymer synthesis, and chemical processing, setting a benchmark for future research in ternary flow systems.