Lattice Boltzmann Simulations of Droplet formation in confined Channels with Thermocapillary flows

TL;DR

This study uses lattice Boltzmann simulations to investigate how thermocapillary effects influence droplet formation and break-up in microfluidic T-junctions, revealing how temperature gradients alter droplet dynamics.

Contribution

It introduces a mesoscale simulation approach to analyze thermocapillarity's role in droplet break-up mechanisms in confined channels, expanding understanding of flow regimes.

Findings

Thermocapillarity significantly affects droplet break-up timing.

Temperature gradients can delay or promote droplet formation.

Scaling laws help predict droplet size post-break-up.

Abstract

Based on mesoscale lattice Boltzmann simulations with the "Shan-Chen" model, we explore the influence of thermocapillarity on the break-up properties of fluid threads in a microfluidic T-junction, where a dispersed phase is injected perpendicularly into a main channel containing a continuous phase, and the latter induces periodic break-up of droplets due to the cross-flowing. Temperature effects are investigated by switching on/off both positive/negative temperature gradients along the main channel direction, thus promoting a different thread dynamics with anticipated/delayed break-up. Numerical simulations are performed at changing the flow-rates of both the continuous and dispersed phases, as well as the relative importance of viscous forces, surface tension forces and thermocapillary stresses. The range of parameters is broad enough to characterize the effects of thermocapillarity on different mechanisms of break-up in the confined T-junction, including the so-called "squeezing" and "dripping" regimes, previously identified in the literature. Some simple scaling arguments are proposed to rationalize the observed behaviour, and to provide quantitative guidelines on how to predict the droplet size after break-up.