Assessing Effectiveness of Pulsed Input on Mixing Characteristics of Non-Newtonian fluids in T-shaped Channels

TL;DR

This study investigates how pulsed velocity inputs improve mixing efficiency of non-Newtonian fluids in T-shaped microchannels, demonstrating significant enhancement over constant flow methods, especially for shear-thinning fluids.

Contribution

It introduces a pulsed inlet velocity approach to enhance mixing of non-Newtonian fluids in microchannels, with detailed analysis across different rheologies and flow parameters.

Findings

Maximum mixing of 97.6% achieved with pulsed input at 180° phase difference and 5 Hz frequency for shear-thinning fluids.

Pulsed velocity inlet significantly outperforms constant velocity in mixing efficiency.

Mixing indices of 89.1% and 85.2% for Newtonian and shear thickening fluids, respectively.

Abstract

Mixing of reagents in microfluidics is necessary for various applications however, due to the laminar nature of flows, efficient mixing in a small span of length and time becomes difficult. The analysis of mixing of non-Newtonian fluids is critical as they are commonly encountered in practical applications. Towards this, we investigated an effective way for mixing of non-Newtonian fluids using pulsatile velocity inlet conditions. In the present study, the non-Newtonian fluid is modelled using the power law model with varying fluid rheology from shear thickening to shear thinning. For enhancing the mixing, pulsed velocity inlet condition is applied with varying phase angle and frequency and compared with constant velocity inlet condition. We demonstrated enhanced mixing using pulsing velocity inlet condition and achieved a maximum mixing of 97.6% using pulsed input velocity with a phase difference of 180{\deg} and considering a frequency of 5 Hz for the case of shear-thinning fluid (n=0.6). For the same condition, the mixing index is 89.1% and 85.2% for Newtonian and shear thickening fluid (n=1.4), respectively. The present study will be helpful in designing micromixers for mixing non-Newtonian fluid effectively in a small span of length and time.