CFD study on Taylor bubble characteristics in Carreau‐Yasuda shear thinning liquids

Abstract

In the present study, Taylor bubble formation in two‐phase gas‐non‐Newtonian Carreau liquid flowing through a confined co‐flow microchannel is investigated. Systematic analyses are carried out to explore the influences of rheological properties, inlet velocities, and surface tension on Taylor bubble length, shape, velocity, and liquid film thickness. Aqueous solutions of carboxymethyl cellulose (CMC) with different mass concentrations are considered as the non‐Newtonian liquids to understand the fundamentals of flow behaviour. With increasing solution viscosity and liquid phase inlet velocity, Taylor bubble formation frequency and velocity increased; however, the bubble length was found to decrease. Velocity profiles inside the Taylor bubble and liquid slug were analyzed, and distinct velocity distributions were found for different CMC concentrations. Flow regime maps are developed based on gas and liquid velocities for Carreau liquids in the co‐flow microchannel. This study essentially provides useful guidelines in designing a non‐Newtonian microfluidic system for precise control and manipulation of Taylor bubbles.

Numerical Insights on Controlled Droplet Formation in a Microfluidic Flow-Focusing Device

“…These relations are similar to the previously reported results for various gas−liquid and liquid−liquid systems but with different prefactor and exponent. 21,62,63 Additionally, a unified scaling relation (L D / W c = 0.244 Ca −0.430 ) is formulated to encompass the studied range of Ca resulting from the variation of interfacial tension, and it shows sound agreement with a maximum deviation of 24%. Droplet velocity is found to increase with increasing Ca (i.e., decreasing interfacial tension) for all cases, as shown in Figure 8b.…”

Dynamics of a Taylor bubble through a shear-thinning fluid up to finite capillary numbers

“…This new theory, however, has not been validated yet with experimental or numerical data. Up to now, numerical simulations of Taylor bubbles moving into realistic shear-thinning fluids are limited to the works of Moreira et al [33] and Sontti and Atta [34]. Without a https://doi.org/10.1016/j.jnnfm.2023.105003 Received 28 August 2022; Received in revised form 24 January 2023; Accepted 30 January 2023 consistent set of experiments or simulations, it is not possible to prove or disprove the theoretical predictions of Picchi et al [32].…”

Modeling the motion of a Taylor bubble in a microchannel through a shear-thinning fluid

“…Thus, we solve the Carreau constitutive model [32], which includes an additional term for the viscosity at zero shear rate, and, therefore, it overcomes the limitations of the power-law viscosity model [33]. The solution of the Carreau model introduces further novelty in our works because the application of this constitutive equation in microfluidics is scarce: the current studies on the bubble hydrodynamics in Carreau fluids [34,35,36,37,38,39] limit their results to a single fluid (carboxymethylcellulose) and are valid below the tested operating conditions.⇥…”