Deformation of soap films pushed through tubes at high velocity

Benjamin Dollet (1) , Isabelle Cantat (1)

1 IPR - Institut de Physique de Rennes

The behaviour of soap films pushed through tubes at large velocities, up to several m/s, is investigated. The film shape deviates from its equilibrium configuration perpendicular to the walls and gets curved downstream. A simple model relates the radius of curvature of the film to the friction in the lubrication films touching the wall, and the scaling of Bretherton (1961) holds up to surprisingly high velocities, at which the capillary and Weber numbers are no longer small parameters. The tube geometry is varied and accounted for through the notion of hydraulic diametre. A limit of stability of the film, beyond which the films burst or evolve unsteadily, is predicted, and captures quantitatively the observations. The new questions raised by our results on the dissipation in soap films are discussed, especially the role of Plateau borders and inertial effects.

Domaines: Matière Molle [cond-mat.soft]

Benjamin Dollet, Isabelle Cantat. Deformation of soap films pushed through tubes at high velocity. Journal of Fluid Mechanics, 2010, 652, pp.529-539. ⟨10.1017/S0022112010000935⟩. ⟨hal-00990004⟩