Analysis of fluid-structure interaction in micromixers with vibrating walls

Abstract

Rapid mixing in micro-channels plays a significant role in the chemical, biological and medical fields. The majority of microfluidic applications is encountered in very low Reynolds number regime. Thus, two reactive fluids are predominantly parallel when they flow along the length of the microchannel. Generally, obstacles or surface modifications are made in the flow path to increase mixing of the fluids. With the development of deformable and flexible micro-channels, the focus has now shifted to the development of micromixers with moving or vibrating walls. In the present work an attempt has been made to numerically model the working of a micromixer with vibrating walls. This has been accomplished by computationally solving the coupled set of equations governing the elasticity of the walls and fluid motion (Fluid structure Interaction). Mixing index, which is a measure of effectiveness of mixing is calculated based on the species concentration at a particular region of interest. External sinusoidal vibrations are applied on the walls of the microchannel of size 225 μm. The effect of vibration on mixing index is studied. Optimization study is taken up to obtain the optimal value of vibration amplitude and frequency to achieve enhanced mixing with reduced pressure drop. The optimal parameters so obtained are observed to function well in the Reynolds number range 0.5-50 in which the entire numerical analysis has been carried out.