16 research outputs found
The relation of steady evaporating drops fed by an influx and freely evaporating drops
We discuss a thin film evolution equation for a wetting evaporating liquid on
a smooth solid substrate. The model is valid for slowly evaporating small
sessile droplets when thermal effects are insignificant, while wettability and
capillarity play a major role. The model is first employed to study steady
evaporating drops that are fed locally through the substrate. An asymptotic
analysis focuses on the precursor film and the transition region towards the
bulk drop and a numerical continuation of steady drops determines their fully
non-linear profiles.
Following this, we study the time evolution of freely evaporating drops
without influx for several initial drop shapes. As a result we find that drops
initially spread if their initial contact angle is larger than the apparent
contact angle of large steady evaporating drops with influx. Otherwise they
recede right from the beginning
The effect of gravity and shear stress on a liquid film driven in a horizontal minichannel at local heating
The present study is focused on the investigation of gravity effect on thermocapillary deformations in a film flowing under action of co-current gas flow, which creates the tangential force on the gas-liquid interface. The influence of local heating intensity on the heater at a substrate is also investigated. Effects of surface tension, temperature dependent viscosity and thermocapillarity are taken into account. Investigations have shown that gravity has a significant effect on the film deformations and pattern. Decreasing of gravity level leads to a flow destabilization. 3D liquid film pattern noticeably changes in spanwise direction. Increasing of heat flux leads to increasing of liquid film deformations. Dependence of film thinning on heat flux is strongly nonlinear. The most dangerous deformations (regions of minimum film thickness with possible disruption of liquid) take place behind the downstream edge of the heater at any gravity conditions.En ligne: http://www.springerlink.com/content/j207456083166646/info:eu-repo/semantics/publishe
Interfacial balance equations for diffusion evaporation and exact solution for weightless drop
Introducing of additional terms into the balance equations to specify the conditions at the interface allows to study physical phenomena in the diffusion evaporation (condensation) of the liquid into the neutral gas. We have taken into account the vapour dynamic effects on evaporating liquid, as well as the waste of energy on deformation of the boundary, changing of the interfacial temperature (the interface has an internal energy and therefore heat capacity), to overcome the surface tension etc. This paper presents the balance conditions at the interface with the diffusion evaporation of the liquid into the neutral gas, for the case when the vapour is considered as an impurity in the gas phase. The analysis of the dimensionless criteria is carried out. The areas of parameters for which the effect of some physical factors take a place have been defined. The exact solution of the diffusion evaporation for a spherical drop at zero gravity conditions has been constructed. The explicit expression for the interfacial temperature and evaporation rate were derived. Solution for evaporation rate coincides with the solution obtained by Maxwell (1890). © Springer Science+Business Media B.V. 2011.SCOPUS: ar.jinfo:eu-repo/semantics/publishe