Ratchet flow of thin liquid films induced by a two-frequency tangential forcing

• Published in: Physics of fluids (1994) Vol. 30; no. 2
• Main Authors: Sterman-Cohen, Elad, Bestehorn, Michael, Oron, Alexander
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.02.2018
• Subjects: Asymmetry; Dependence; Flow velocity; Fluid dynamics; Fluid inertia; Oil films; Periodic variations; Physics; Substrates; Taylor instability; Thin films
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/1.5010262

A possibility of saturating Rayleigh-Taylor instability in a thin liquid film on the underside of a substrate in the gravity field by harmonic vibration of the substrate was recently investigated [E. Sterman-Cohen, M. Bestehorn, and A. Oron, Phys. Fluids 29, 052105 (2017); Erratum, Phys. Fluids 29, 109901 (2017)]. In the present work, we investigate the feasibility of creating a directional flow of the fluid in a film in the Rayleigh-Taylor configuration and controlling its flow rate by applying a two-frequency tangential forcing to the substrate. It is shown that in this situation, a ratchet flow develops, and the dependence of its flow rate on the vibration frequency, amplitude, its periodicity, and asymmetry level is investigated for water and silicone-oil films. A cause for the emergence of symmetry-breaking and an ensuing flow in a preferred direction is discussed. Some aspects of a ratchet flow in a liquid film placed on top of the substrate are discussed as well. A comparison with the case of a neglected fluid inertia is made, and the differences are explained.