Viscous influences on impulsively generated focused jets

TL;DR

This paper investigates how viscosity influences the formation and velocity of impulsively generated focused jets, combining experiments and simulations to develop predictive models relevant for biomedical and manufacturing applications.

Contribution

It provides new insights into viscous effects on free surface jet dynamics and introduces an equation to predict viscous jet velocity, filling a gap in existing research.

Findings

Viscosity reduces jet speed through shear flow and vorticity diffusion.

Mass and momentum transfer along the free surface are key to jet formation.

An equation predicting viscous jet velocity is proposed.

Abstract

Impulsively generated focused jets play a significant role in various applications, including inkjet printing, needle-free drug delivery, and microfluidic devices. As the demand for generating jets and droplets from medium to highly viscous liquids increases, understanding the role of viscosity in jetting dynamics becomes crucial. While previous studies have examined the viscous effects on walls, the impact on free surfaces has not been thoroughly understood. This study aims to bridge this gap by integrating experiments with numerical simulations to investigate the viscous effects on focused jet formation. We demonstrate that mass and momentum transfer along the tangential direction of the free surface contribute to focused jet formation, and viscosity plays a key role in this transfer process. The viscosity-induced diffusion of the shear flow and vorticity near the free surface reduces the jet speed. Based on experimental observations and simulation results, we propose an equation to predict the viscous jet velocity. These findings offer new perspectives on viscous interface dynamics in advanced manufacturing and biomedical applications.