Dieter BOTHE, viendra donner un séminaire le jeudi 18 mai 2017, à 14h30 dans l'amphithéâtre A301 du Pôle API à Illkirch.
Titre : Modeling and VOF-based simulation of transport processes at fluid interfaces
Résumé : Besides the already rich hydrodynamics of two-phase flows, additional transport and transfer processes like heat or mass transfer, Marangoni effects as well as phase change phenomena, are of utmost importance in many applications with fluid interfaces. The present talk surveys different recent developments for modeling and simulating several small-scale phenomena occurring at liquid films, droplets and gas bubbles. The work is based on the sharp-interface continuum mechanical approach with different levels of complexity concerning physico-chemical interface properties, where special attention is devoted to thermodynamic consistency. The latter is especially relevant in dynamic situations far away from thermodynamic equilibrium, when interfacial jump conditions need to be considered in sufficient generality and only be simplified according to scale considerations.
Our numerical approaches and techniques build mainly on the Vol-ume of Fluid (VOF) method, since the latter allows for sufficiently accurate phase volume conservation, respectively correct phase volume changes if phase transfer is included. In many cases, VOF and other methods allow for Direct Numerical Simulations (DNS) of elementary sub-processes like droplet or bubble motion with deformable interfaces, binary droplet collisions, film flow etc., where we define a DNS to be a fully resolved numerical computations without built-in scale-reduction or other model simplifications. On the other hand, even for such elementary sub-processes, local small-scale features can appear which are relevant for a sound description but cannot be resolved or require unaffordable numerical effort. We will discuss several such examples, including falling film flow, binary droplet collisions as well as mass transfer at rising gas bubbles where we also report on techniques which allow overcoming these computational problems in some prototypical situations.
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