Analysis and simulations of droplet generation regimes in a coaxial microfluidic device

TL;DR

This paper evaluates the Basilisk software for predicting droplet generation in microfluidic devices, validates it against theoretical and experimental data, and proposes new scaling laws for droplet size prediction.

Contribution

It introduces validated numerical simulations of droplet formation regimes and refines scaling laws by incorporating additional physical effects.

Findings

Basilisk accurately predicts droplet dynamics in microfluidic flows.

New scaling laws improve droplet size prediction in dripping and jetting regimes.

Flow parameters significantly influence droplet formation and size.

Abstract

The generation of microdroplets via segmentation in microfluidic devices is of interest in many applications, from biochemical to pharmaceutical. This technique permits indeed much higher control on the droplet size, uniformity and generation rate than in standard batch generation processes. In this work we have evaluated the suitability of the open-source software Basilisk to accurately predict microdroplet generation by segmentation. We have validated the numerical tool with analytical solutions for the dynamics of droplets in confined flows, namely with Bretherton theory, and by comparison with literature experimental results. We have then performed several campaigns of numerical simulations for a coaxial device, analyzing the different regimes of droplet generation, and evaluating how the physical and flow parameters affect the production mechanisms and {the diameters of the generated droplets}. Finally we have proposed new scaling laws for the prediction of droplet diameters in the dripping and jetting regimes, refining existing ones by taking into account additional physical effects, like the viscosity ratio.