Soap Films Burst Like Flapping Flags

Henri Lhuissier (1) , Emmanuel Villermaux (1, 2)

1 IRPHE - Institut de Recherche sur les Phénomènes Hors Equilibre
2 IUF - Institut universitaire de France

When punctured, a flat soap film bursts by opening a hole driven by liquid surface tension. The hole rim does not, however, remain smooth but soon develops indentations at the tip of which ligaments form, ultimately breaking and leaving the initially connex film into a mist of disjointed drops. We report on original observations showing that these indentations result from a flaglike instability between the film and the surrounding atmosphere inducing an oscillatory motion out of its plane. Just like a flag edge flaps in the wind, the film is successively accelerated on both sides perpendicularly to its plane, inducing film thickness modulations and centrifuging liquid ligaments that finally pinch off to form the observed spray. This effect exemplifies how the dynamics of fragile objects such as thin liquid films is sensitive to their embedding medium.

Mots clés: Sheets; Aureole; Dynamics; Surface-tension; Thil liquid-films

Domaines: Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Henri Lhuissier, Emmanuel Villermaux. Soap Films Burst Like Flapping Flags. Physical Review Letters, 2009, 103 (5), pp.054501. ⟨10.1103/PhysRevLett.103.054501⟩. ⟨hal-00426813⟩