Liquid film burst caused by perpendicularly blowing gas jet

Abstract

Blowing gas perpendicularly onto a liquid film may lead to various kinds of film deformations. When the jet is steady and mild, a protrusion structure will appear on the film and stretches in length, as jet velocity continue to increase, separated bubbles will detach from the protruded surface. Compared with continuously blowing gentle gas jets, short duration pulsed strong jets are more realistic and generally existing, yet the in-depth mechanism studies are insufficient, thus need further investigation. We have observed that the liquid film protrusion tends to stretch to a critical length then burst into tiny droplets when blown by the pulsed jet. After theoretical analysis, we discover that during the stretching process, rather than the jet velocity that was presumed as the driving factor, the two physical properties of the fluid, namely the surface tension and viscosity, play the dominant role to cause the structure collapsing. The critical burst length of the protrusion structure correlates with the ratio of these two properties. We conducted experiments using various test fluids, gas nozzle diameters, and jet velocities. The experimental results confirmed our theoretical analysis. This discovery provides a critical insight into the physics of liquid film deformation and atomization under gaseous crossflow, which can be commonly seen in fuel injection and aerosol droplet generation related fields.