Marangoni instabilities for convective mobile interfaces during drop exchange: Experimental study and CFD simulation

[Display omitted] ► Experimental results indicate a significant delay in onset of Marangoni convection. ► The simulation results show an immediate Marangoni convection. ► Quasi-static isotherm equations cannot be simply applied for the mobile interfaces. The inflow pattern of liquid into a droplet i...

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Vydáno v:Colloids and surfaces. A, Physicochemical and engineering aspects Ročník 441; s. 846 - 854
Hlavní autoři: Javadi, A., Karbaschi, M., Bastani, D., Ferri, J.K., Kovalchuk, V.I., Kovalchuk, N.M., Javadi, K., Miller, R.
Médium: Journal Article
Jazyk:angličtina
Vydáno: Elsevier B.V 20.01.2014
Témata:
adsorption
Capillary pressure tensiometry
Coaxial double capillary
Computational fluid dynamics
Delay
Drop flow visualization
Droplets
Dynamic surface tension
Instability
Marangoni instability
Mathematical models
Mobile liquid interface
Multicomponent CFD simulation
Profile analysis tensiometry
Simulation
Stability
Surface chemistry
surface tension
surfactants
Coaxial double capillary
Dynamic surface tension
Profile analysis tensiometry
Mobile liquid interface
Capillary pressure tensiometry
Multicomponent CFD simulation
Drop flow visualization
Marangoni instability
ISSN:0927-7757, 1873-4359
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Shrnutí:[Display omitted] ► Experimental results indicate a significant delay in onset of Marangoni convection. ► The simulation results show an immediate Marangoni convection. ► Quasi-static isotherm equations cannot be simply applied for the mobile interfaces. The inflow pattern of liquid into a droplet is studied experimentally using a surface active dye and compared with results of CFD simulations. The results show visual agreement between experiments and simulations. The CFD simulations show also good agreement with the surface tension measured by drop profile analysis tensiometry (PAT). The inflow of the surfactant induces a Marangoni instability caused by the local arrival of the surfactant at the drop surface. The onset of this Marangoni instability observed experimentally has a delay of about 10s when compared with the simulation results. Different scenarios are discussed, including a boundary layer barrier, a kinetic-controlled adsorption mechanism, the way of renewing a mobile interface, and a critical Marangoni number required for the onset of such instability. It turns out that besides the commonly defined critical Marangoni number, the main reason for delay of Marangoni instability is possibly the mobility of the drop surface which can prevent the establishment of a quasi static adsorbed layer required for the appearance of such surface effect.
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ISSN:0927-7757
1873-4359
DOI:10.1016/j.colsurfa.2012.10.032