Скачать или смотреть Fluid Mechanics Webinar Series – Gallaire

We revisit the canonical Rayleigh-Taylor instability and investigate the case of a thin film of liquid continuously flowing down the underside of an inclined plane. The presence of a natural flow along the plane competes with the conventional droplet forming instability and gives rise to an intricate pattern formation, which is studied experimentally, numerically and theoretically using the lubrication equation. We observe the prevalence of streamwise-invariant structures, modulated along the transverse direction perpendicular to the flow direction, called rivulets. We determine the universal thickness profile towards which they saturate and explore the origin of this pattern selection by analyzing the impulse response as well as the response to localized defect on the substrate. We eventually discuss the role of these hydrodynamic instabilities on the morphogenesis of some typical karst draperies structures encountered in limestone caves.