Seminar über aktuelle Fragen zur Dynamik komplexer Fluide: Numerical simulation of multi-component droplets
10:15 - 11:15
Dr. Christian Diddens
Technische Universiteit Eindhoven, The Netherlands
Max-Planck-Institut für Dynamik und Selbstorganisation (MPIDS)
Droplets are ubiquitous in nature and relevant for a widespread range of technologies like e.g. inkjet printing.
While the dynamics of pure droplets are well understood, the situation drastically changes when the droplet composition is constituted by a mixture of different liquids. For an evaporating multi-component droplet, e.g., the different volatilities of the components induce solutal gradients and due to composition-dependent liquid properties, intriguing phenomena can be observed: While a non-constant surface tension can drive regular or chaotic solutal Marangoni flow, which competes with the thermal Marangoni flow induced by the latent heat of evaporation, a difference in the mass densities of the constituents can give rise to significant natural convection in the droplet, even below the millimeter scale. In case of composition-dependent miscibility, an evaporation-induced
phase separation can be triggered, creating e.g. oil microdroplets in an evaporating Ouzo droplet.
Finally, if as in the case of inkjet printing, multiple droplets of different compositions are assembled on a substrate, the internal flow can be reversed by interaction through the vapor phase and coalescence of different droplets can be delayed and highly asymmetric.
All afore-mentioned aspects are discussed on the basis of finite element or lubrication theory simulations and supported by experimental data.