Lattice Boltzmann Simulation For The Mixing Of Binary Fluid In Micro Channel

Mixing of binary fluids in a micro mixer is one of the most basic and revealing cases in the general subject of micro fluidics. Due to the micro scale, the binary fluids flow is typically laminar, the diffusion is dominant, and it would take quite long time to get well mixed.Generally, application fields of Mixing in a micro mixer encompass both modern, specialised issues such as sample preparation for chemical analysis and traditional, widespread usable mixing tasks such as reaction, gas absorption, emulsification, foaming, and blending. Therefore Mixing of binary fluids in a micro mixer is of great significance.As the internal structure of the micro mixer is very complex and the governing equations are highly nonlinear, some of the flow properties are extremely difficulty to determine accurately with theoretical method. Moreover, it is difficult to read the tiny difference in micro mixing effect in the laborary with the observation method. With the development of computer technology, computational fluid dynamics (CFD) methods have gradually made it possible to directly solve many complex fluid dynamic problems.In recent years, the lattice Boltzmann method (LBM) has developed into promising numerical scheme for simulating fluid flows and modeling physics in fluids. The scheme is particularly successful in fluid flow applications involving simulations of multiphase and multicomponent flows and complex boundaries and so on. Compared with the traditional CFD methods, LBM has many unique advantages, such as simple codes, easy implementation of boundary conditions, and fully parallelism. In this dissertation, lattice Boltzmann method is used to study mixing of binary fluids in a micro mixer. The main jobs can be summarized on two dimensions:1. The basic theoretics of LBM:a. Introducing the history and present research situation of the lattice Boltzmann method. (in Chapter 1)b. rigorous derivation and proving process for LBM is given at length. (in Chapter 2)c. several kind of typical boundary condition in the lattice Boltzmann method are discussed such as bounce back boundary, specular reflection boundary, extrapolation method, periodic boundary, pressure and velocity boundary. (in Chapter 3)d. the lattice Boltzmann model for binary mixtures proposed by Luo and Girimaji is produced particularly.2. The problem of mixing in micro mixer:a. Introducing the present research situation of the problem of mixing in micro mixer.(in Chapter 1,4)b. Introducing mixing principles, means to induce mixing, determination of mixing efficiency.(in Chapter 4)c. Proposed a new passive micro mixer to affect mixing by changing the hydrophobic and hydrophilic properties of the substrate surface, and numerically studied the effect of viscosity and viscosity difference and boundary patterned slip on mixing in the micro mixer using lattice Boltzmann method (LBM). It has been found that it is feasible to optimize the micro mixer design by combining the viscosity effect and boundary patterned ratio altogether. (in Chapter 4)d. Proposed another passive micro mixer with obstacle disturbance. (in Chapter 4)e. Proposed a novel, simple and convenient active micro mixer using time pulsing, and the essential factors for the mixing are discussed. It has been found that the chaos in T type micro mixer can be induced easily through controling the fluids velocity in inlets. (in Chapter 4)...