Effect of micro-channel geometry on fluid flow and mixing

Abstract

Understanding the flow fields at the micro-scale is key to developing methods of success-fully mixing fluids for micro-scale applications. This paper investigates flow characteristics and mixing efficiency of three different geometries in micro-channels. The geometries of these channels were rectangular with a dimension of; 300 m wide, 100 m deep and 50 mm long. In first channel there was no obstacle and in the second channel there were rectangular blocks of dimension 300 m long and 150 m wide are placed in the flow fields with every 300 m distance attaching along the channel wall. In the third geometry, there were 100 m wide fins with 150° angle which were placed at a distance of 500 m apart from each other attached with the wall along the 50 mm channel. Fluent software of Com-putational Fluid Dynamics (CFD) was used to investigate the flow characteristics within these microfluidic model for three different geometries. A species 2D model was created for three geometries and simulations were run in order to investigate the mixing behaviour of two different fluid with viscosity of water (1 mPa s). Models were only built to investigate the effect of geometry, therefore only one fluid with similar viscosity was used in these models. Velocity vector plots were used in the CFD analysis to visualise the fluid flow path. Mass fractions of fluid were used to analyse the mixing efficiency. Two different col-ours for water were used to simulate the effect of two different fluids. The results showed that the mixing behaviour strongly depended on the channel geometry when other parameters such as fluid inlet velocity, viscosity and pressure of fluids were kept constant. In two geometries lateral pressure and swirling vortexes were developed which provided better mixing results. Creation of swirling vortexes increased diffusion gradients which enhanced diffusive mixing.

Numerical analysis of mixing performance in sinusoidal microchannels based on particle motion in droplets

“…Furthermore, in channels with larger central radius, vertical displacement of two different particles had similar trajectories which is not desired for mixing. As the channels scale down, trajectory variation between two particles released at the same location increased, which validates the experimental results in the literature that show faster mixing in sinusoidal channels with smaller central radius (Naher et al 2011). In straight channels, particle path in droplets did not change significantly in vertical direction which proves the necessity of the sinusoidal shape to increase the mixing rate.…”

Semiconductor Materials Optimization for a TFET Device With Central Nothing Region on Insulator

“…The simulations of new nanostructures are useful for the design and fabrication process, [20], [21]. Our simulations are performed in Atlas from Silvaco.…”

Effects of ionic concentration gradient on electroosmotic flow mixing in a microchannel

“…Most of them focused on enhancing the efficiency of mixing by passive or active methods. For passive mixers, complex channel geometries were used to increase the interaction area between the mixing liquids to achieve complete mixing within a short transport distance [3]- [6]. On the other hand, active mixing methods introduce external energy sources into the mixing process to enhance the mixing efficiency [6] [7].…”