Visualization study on the transient liquid film behavior and inner gas flow after rupture of a soap bubble

Abstract

This study examined the transient behavior of liquid films and the flow of inner gas. Olive oil particles were inserted into a soap bubble through a Laskin nozzle for visualization, and the inner gas flow fields were measured by time-resolved particle image velocimetry. A pulse laser was used for contactless rupturing of the soap bubble. The transient behavior of the liquid film after the soap bubble ruptured was captured using a high-speed camera at 3,600 frames per second. After rupturing the soap bubble, the inner gas flowed out to the outside through the crack. This is called the primary flow. The removal velocity of the upper liquid film was faster than that of the bottom liquid film. The Kelvin–Helmholtz vortex was generated at the upper and bottom boundaries of the liquid film. A series of Kelvin–Helmholtz vortices, which arise in shear flow along a contact discontinuity, were formed around the bubble sphere. Secondary flow was generated due to a change in momentum after impinging the soap film to a point, and was faster than primary flow.