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 film is exposed to side-wind, the beads are pushed downstream breaking the symmetry 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.