Structures of a Continuously Fed Two-Dimensional Viscous Film under a Destabilizing Gravitational Force

Abstract

We study the gravity induced instability of a liquid film formed below a plane grid which is used as a porous media in an original hydrodynamic experiment. The film is continuously supplied with a controlled flow rate. We give through a phase diagram the full spectrum of the different flow regimes and we investigate the dynamics of the observed structures. True secondary instabilities of a 2D periodic pattern are described. The control parameters are the flow rate and the viscosity.

Destabilization of a Viscous Film Flowing Down in the Form of a Vertical Cylindrical Curtain

“…The continuously fed film behavior is similar to the one observed in the 2D case [12] where liquid columns and sheets are successively obtained at increasing flow rates. So we clearly observe in the present experiment a Fig.…”

“…The present study departs from the previous approaches cited above by adapting the two-dimensional (2D) experimental setup used previously to investigate the destabilization of a liquid film [12]. The current research, in a lower dimensionality, analyses the spatiotemporal behavior of a film in sheet regime.…”

“…3(a)]. In this connection, previous studies [11][12][13] have reported that column oscillations are a generic response in this regime. Indeed, radial oscillations of curtain base, primarily induced by competition between gravity and surface tension, are actually observed only for values of near RT , chosen as a reference gap.…”

“…In this way, any incoming fluid flows through the whole annulus and a uniform laminar film is formed below it. As in the 2D case [12], the steel grid is 1 mm in thickness, with circular holes of 1 mm in diameter arranged on a 2 mm regular, hexagonal lattice. The ability to change annulus width, by varying the radius of the inner and outer masks, is one of the novelties of this experimental setup.…”

Faraday wave lattice as an elastic metamaterial

“…Similar oscillatory motions were observed and characterized in 1D systems such as Taylor-Couette [23], falling liquid columns [24], Rayleigh-Bénard convection rolls [25], and viscous fingering [26]. Very few 2D systems exhibit this kind of secondary oscillatory modes: vibrated granular materials [27], liquid columns [28] and bouncing droplets crystalline aggregates [29].…”