Influence of wind on a viscous liquid film flowing down a thread

Abstract

We investigate experimentally the effect of wind on the dynamics of a viscous liquid film flowing down a thread. The liquid film is well known to destabilize into an axisymmetric bead-like pattern in stagnant air. When the flowing thin film is exposed to side wind, the beads are pushed downstream of the wind, breaking the symmetry and leading to a modification of the film flow. The viscous dissipation in the liquid film decreases with increasing side wind, leading to a faster slide speed of the liquid beads. The inertia in the film is then increased, which can induce a regime shift, triggering an instability. When the film becomes unstable, it switches from a periodic pattern of equally sized liquid beads to an irregular film pattern where large beads collide with smaller ones.