Study of falling liquid film stability with negative gravity

Abstract : A film of condensation that forms on a cold ceiling is unstable with respect to gravity (called negative gravity) and breaks down into a myriad of regularly spaced droplets, the distance of which can be predicted by linear stability analysis ; this is referred to the well-known Rayleigh-Taylor instability. In the case of a slight inclination, the film flows in the direction of the slope and the symmetry is broken. Another type of instability can arise in this case, which produces travelling wave structures, like on a windshield of a car under rain fall ; this is referred to the hydrodynamic instability. The coupling of the two above-mentionned instabilities has never been studied, despite the fact that it is of great interest, not only on the fundamental point of view, but also on a practical point of view. Indeed, many industrial processes involving falling films (evaporators, cooling systems, bioreactors) have inclined surfaces where wave structures play a crucial role, not only in the stability of the film but also in the heat and mass transfer processes. The objective of this project will be from a dedicated low-dimension theoretical model, to determine the phase diagram of such a complex system, using linear and non-linear analytical analysis, together with numerical simulations. The model will then be validated with experimental data obtained from an in-house experimental set-up.
Promoteur/Supervisor : Prof. Scheid Benoit
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Centre de recherche/Research center : TIPs
Faculté/Faculty : Faculté des Sciences appliquées - école polytechnique/Brussels School of Engineering (Faculty of Applied Sciences)
Ecole doctorale/Graduate Colleges : Sciences de l'ingénieur/Engineering
Ecole doctorale thématique/Graduate School (French Only): Phénomènes non-linéaires, systèmes complexes et mécanique statistique

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