Thermocapillary convection and interface deformation in a liquid film within a micro-slot with structured walls

Abstract

Thermocapillary convection in a thin liquid film inside a micro-slot with structured walls kept at different temperatures is studied. The liquid film is wetting the substrate wall and is separated from the cover wall by a gas layer. If the slot walls are structured, the temperature at the liquid-gas interface is non-uniform. The temperature variation induces thermocapillary stresses which bring the liquid into motion and lead to the interface deformation. We investigate the film flow inside the micro-slot, the heat transfer, the liquid-gas interface deformations and the film stability in the framework of the long-wave theory. We show that the amplitude of the interface deformation increases with increasing of the wall structure period. We demonstrate that the structured walls lead to the heat transfer enhancement, which effect is for the studied range of parameters stronger if the cover wall is structured. We also show that the wall structure enhances the long-wave Marangoni instability. The destabilizing effect of the substrate structure is stronger than that of the cover wall structure.

Nonlinear dynamics of confined thin liquid-vapor bilayer systems with phase change

“…Two vortices rolling in opposite directions emerge within one hump of the liquid phase which resembles the velocity field inside a liquid film subjected to the Marangoni effect. 30,31,37 However, in the present system, the vortices in the liquid phase shown in Fig. 7 are not induced by thermocapillarity, because setting the Marangoni number to zero yields almost the same velocity field ͑not shown͒.…”

“…24 The vortices in the framework of the long-wave theory were reported in Ref. 31 and also in a study of falling liquid films on corrugated surfaces. 35 In Ref.…”

“…We discuss the possibility of the emergence of nontrivial nonruptured stationary states. The difference from the other Marangoni-driven bilayer systems [28][29][30][31] and "thick" bilayer systems with phase change 18,19,22,33 is emphasized.…”

“…Here, the vapor pressure serves as an active source of the liquid dynamics. This vapor-pressure-induced mechanism was not considered in bilayer systems without phase change, [28][29][30][31] where the gas dynamics was ignored and only the heat conduction in the gas phase was considered. Strictly speaking, the variation of the vapor pressure was taken into account in the model of film boiling.…”

Marangoni-induced deformation of evaporating liquid films on composite substrates

“…Thermocapillary convection and film deformation on a heated substrate can be influenced by using substrates with topography [13][14][15][16][17]. If the substrate temperature is higher than that of the environment, the sites on the liquid-gas interface over the topography crests are hotter than the interface sites corresponding to the topography troughs.…”