Numerical investigation of fluid flow through microchannel

Abstract

Computer simulations of fluid dynamics problems involving microscale surface interactions are of both fundamental and practical importance in the development of Micro-Electro-Mechanical Systems and Lab-on-Chip devices. This thesis depicts how electro osmotic liquid flow, which is one of the electro kinetic effects, is numerically investigated, through different micro channels. A mathematical model for the electro osmotic flow that consists of a two-dimensional Poisson-Boltzmann equation and a two dimensional Navier-Stokes equation governing the Electric Double Layer (EDL) field is developed. A numerical solver using Galerkin algorithm is created, using the algebra package MAPLE. This solver is implemented in square microchannels to investigate the factors that affect the flow behaviours. The numerical analysis shows the influences of the channel size, the ionic concentration and the applied electrical field strength on the velocity distribution and potential distribution. The electroosmotic liquid flow through convergent divergent microchannel is also modelled using Poisson-Boltzmann equation and Navier Stokes equation in polar coordinates. This model is solved using COMSOL multiphysics package, using partial differential equation mode. The effect of zeta potential and applied electric potential on the velocity distribution is evaluated. Numerical analysis of microscale gas flow through different geometries is also taken for analysis. Because of the different nature of gas and liquid flow in microdevices, a different methodology is implemented in gas flow. A solver in C program is developed to investigate the flow behaviours by using Alternative Direction Implicit Method. The influences of Knudsen number and Reynolds number on the entrance length in rectangular cavity are studied. The effect of Reynolds number on the reattachment length is also proven here. The results are validated using the analytical and numerical results available in the literature. newline newline newline