Lattice Boltzmann Simulation For Complex Fluid

As a mesoscale simulation method Lattice Boltzmann Method (LBM) based on massand momentum conservations is used to simulate the complex fluid, in which Continuity andthe Navier-Stokes equations can be conformed. The derivation of the Navier-Stokes equationfrom Lattice Boltzmann equation is given in detail in this thesis. In order to testify LBMmethod, one of the basic two-dimensional models (D2Q9 model) is employed to simulate thePoiseuille Channel flow and the simulation results are in well agreement with those from theanalytical solution. Free energy LBM is used as a development of the basic model to simulate vapor-liquidtransition and phase separation of binary blends. Our studies focused on the binary blendssystem under the shear boundary condition, and obtained the following results: 1.In the simulation of one-component vapour-liquid system, we got convincing results which are consistent with theoretical results and testified the critical temperature. It is revealed that temperature is the dominant factor that determines morphologies of phase domains and interfacial width. Furthermore, various phase structures at the equilibrium state can be obtained by varying initial concentrations. 2.The simulation results for binary blends under periodic boundary condition reveal that temperature determines the density distribution at equilibrium state and viscosity determines the smooth degree of phase boundary and composition controls the morphology of phase domains. 3.The simulation results for binary blends under shear boundary condition reveal that at a given shear velocity there exists the competition between shear and component repulsion. In low viscosity and strong repulsion system, it is the repulsion effect that mainly determines the morphologies at equilibrium state; in the system with low viscosity and weak repulsion, the dominant factor is the shear. However, in system with low viscosity and weak repulsion, we observed a characteristic time. Before that time the repulsion effect dominates the phase separation, thereafter it is the shear that dominates the phase separation. Due to the competition, binary blends systems with different viscosities and interaction parameters will form lamella morphologies with different thicknesses.