Viscosity effects in oscillatory liquid levitation

Liquids under vertical oscillation can remain levitated above a gas layer despite the classical Rayleigh–Taylor instability, but the role of viscosity remains unclear. Here, we experimentally investigate viscosity effects in oscillatory liquid levitation using high-speed imaging. The minimum container amplitude required for stable levitation increases systematically with viscosity, whereas the liquid oscillation amplitude changes only weakly. Viscosity also affects the two interfaces asymmetrically, exerting a weak influence on the lower-interface levitation threshold but a stronger influence on the onset of Faraday waves at the upper surface. These results clarify how dissipative effects shape levitation stability.