Numerical investigation on flow of complex fluid by nonlinear viscosity and elasticity in microchannels

Abstract

Complex fluids are widely transported through micro-scale channels including industrial piping systems such as inkjet printers, heat exchangers using nanofluids, redox flow batteries, 3D printers, and natural piping systems such as the circulatory systems of humans and animals, and crude oil flowing between the cracks of the rocks. These complex fluids are not only transported but also applied in various fields such as mixing, separation of particles, and improvement of the energy efficiency of transportation. Because complex fluids consist of multiple phases, these phases interact with each other, emerging macroscopically as shear-dependent viscosity (nonlinear viscosity) and elasticity. Therefore, it is essential to understand the relationship between the characteristics of complex fluids and the flow structure, flow characteristics, and flow instability in microchannel systems. In this dissertation, the effects of nonlinear viscosity and elasticity on the flow structure, flow characteristics, and flow instability in microchannels are investigated. By using a numerical approach to separately consider nonlinear viscosity and elasticity, the effect of each characteristic on the flow through microchannels can be determined. In addition, the influence of simultaneous nonlinear viscosity and elasticity on the flow is also investigated.