Investigation of viscosity effect on droplet formation in T-shaped microchannels by numerical and analytical methods

Abstract

Both numerical and analytical models have been developed to explore the viscosity effect of the continuous phase on drop formation at a T-shaped junction in immiscible liquids. The effects of the generalized power law coefficient, the power law exponent and the yield stress on the mechanism of drop breakup, final drop size and frequency of drop formation are studied by using the numerical three-dimensional volume of fluid model. Droplets coalescence in Bingham fluids is observed in the beginning transient period. The effect of yield stress on drop extension is also discussed. Predictions of drop size by using an analytical force balance show satisfactory agreement with simulation results for Newtonian and power law fluids with different viscosity ratios. The approximation error associated with the analytical model for Bingham fluids is also acceptable. This analytical model can greatly shorten the prediction time as compared with the numerical model, which is helpful for on-line control.

Experimental investigations of non‐Newtonian/Newtonian liquid‐liquid flows in microchannels

“…The shift in the boundary between the plug and the parallel flows with the polymer addition could be due to both the change in the shear viscosity and the nonNewtonian rheology of the aqueous continuous phase. Sang et al, 32 from numerical analysis of droplet formation, found that an increase in Newtonian viscosity delayed the drop break up at the channel inlet and resulted in a decrease in the area of plug flow in the map. However, when power law fluids were used, as the flow behavior index, n, decreased (or the amount of polymer increased), the droplets broke closer to the Tjunction and extended the region of plug flow.…”

Numerical Simulation of Droplet Dynamics in Membrane Emulsification Systems

“…The static contact angle between the two phases and the wall influences the droplet growth in the dispersed and continuous phase channel. It has been observed that the effect of contact angle in the droplet formation is negligible when its value is greater than 165 o (Sang et al, 2009). The value of static angle used in the present simulation has been set to 170 o .…”

CFD analysis of microchannel emulsification: Droplet generation process and size effect of asymmetric straight flow-through microchannels

“…Computational fluid dynamics (CFD) methods have also been used to simulate and analyze droplet generation in microfluidic channel configurations (Sang et al 2008;Kashid et al 2010; Zhou et al 2006;de Menech et al 2008;Gupta and Kumar 2010).…”