Evaporating pure, binary and ternary droplets: thermal effects and axial symmetry breaking

Abstract

The Greek aperitif Ouzo is not only famous for its specific anise-flavored taste, but also for its ability to turn from a transparent miscible liquid to a milky-white colored emulsion when water is added. Recently, it has been shown that this so-called Ouzo effect, i.e. the spontaneous emulsification of oil microdroplets, can also be triggered by the preferential evaporation of ethanol in an evaporating sessile Ouzo drop, leading to an amazingly rich drying process with multiple phase transitions [H. Tan et al., Proc. Natl. Acad. Sci. USA 113(31) (2016) 8642]. Due to the enhanced evaporation near the contact line, the nucleation of oil droplets starts at the rim which results in an oil ring encircling the drop. Furthermore, the oil droplets are advected through the Ouzo drop by a fast solutal Marangoni flow. In this article, we investigate the evaporation of mixture droplets in more detail, by successively increasing the mixture complexity from pure water over a binary water-ethanol mixture to the ternary Ouzo mixture (water, ethanol and anise oil). In particular, axisymmetric and full three-dimensional finite element method simulations have been performed on these droplets to discuss thermal effects and the complicated flow in the droplet driven by an interplay of preferential evaporation, evaporative cooling and solutal and thermal Marangoni flow. By using image analysis techniques and micro-PIV measurements, we are able to compare the numerically predicted volume evolutions and velocity fields with experimental data. The Ouzo droplet is furthermore investigated by confocal microscopy. It is shown that the oil ring predominantly emerges due to coalescence.

References in corpus (3)

• Evaporation-triggered microdroplet nucleation and the four life phases of an evaporating Ouzo drop
• Formation of surface nanodroplets under controlled flow conditions
• Self-wrapping of an ouzo drop induced by evaporation on a superamphiphobic surface

Cited by in corpus (18)

• Gravitational effect in evaporating binary microdroplets
• Culinary fluid mechanics and other currents in food science
• On explosive boiling of a multicomponent Leidenfrost drop
• Evaporation of a sessile colloidal water-glycerol droplet: Marangoni ring formation
• Concentration Gradients in Evaporating Binary Droplets Probed by Spatially Resolved Raman and NMR Spectroscopy
• Sessile drop evaporation in a gap -- crossover between diffusion-limited and phase transition-limited regime
• Rayleigh-Taylor instability by segregation in an evaporating multi-component microdroplet
• Surface Properties of Colloidal Particles Affect Colloidal Self-Assembly in Evaporating Self-Lubricating Ternary Droplets
• How liquid-liquid phase separation induces active spreading
• Bifurcation tracking on moving meshes and with consideration of azimuthal symmetry breaking instabilities
• Marangoni instability triggered by selective evaporation of a binary liquid inside a Hele-Shaw cell
• Physiochemical hydrodynamics of the phase segregation in an evaporating binary microdroplet
• Evaporating sessile droplets: solutal Marangoni effects overwhelm thermal Marangoni flow
• Contact Angle of an Evaporating Droplet of Binary Solution on a Super Wetting Surface
• Molecular Rotors for In Situ Viscosity Mapping during Evaporation of Confined Fluid Mixtures
• Oscillatory droplet dissolution from competing Marangoni and gravitational flows
• Marangoni flow driven hysteresis and azimuthal symmetry breaking in evaporating binary droplets
• Internal flow and concentration in neighbouring evaporating binary droplets and rivulets