Fluid-fluid and solid -fluid interfacial studies by means of the lattice Boltzmann method

This thesis develops a mean-field free energy lattice Boltzmann scheme to simulate multiphase/multicomponent fluid systems. In this model, both the macroscopic free energy functional and microscopic interactions are represented. Various criteria were examined to validate this multiphase/multicomponent model and good agreement with theoretical predictions was found. Compared with the Swift free energy model, more physical contact angles and fluid density profiles near a solid wall have been obtained.

The important advancement of this model is that the solid-fluid interaction is implemented physically to the lattice Boltzmann method (LBM). Simulations were performed to study several solid-fluid interfacial phenomena, including the wettability on heterogeneous surfaces, droplet self-propelled movements, dynamic wetting, droplet movements in rough and hydrophobic channels, liquid condensation on patterned surfaces, and apparent slip on solid surfaces. The results presented in this thesis demonstrate the potential of this meanfield free energy LBM model in solid-fluid interfacial studies.

In addition, LBM was also employed to investigate the electrohydrodynamic drop deformations under electric field for the first time. Good agreement with theory was obtained, suggesting that LBM could be an attractive alternative for electrohydrodynamic simulations. A modification of the general periodic LBM boundary condition for fully developed periodic flows was also presented. Simulations had shown that the proposed boundary treatment is better than the existing ones in terms of inlet/outlet defects and applicability.