Three-dimensional dynamics of falling films in the presence of insoluble surfactants

Assen Batchvarov , Lyes Kahouadji , Cristian R Constante-Amores , Gabriel Farah , Norões Gonçalves , Seungwon Shin (1) , Jalel Chergui (2) , Damir Juric (2) , Omar K Matar

1 Hongik University
2 LIMSI - Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur

We study the effect of insoluble surfactants on the wave dynamics of vertically-falling liquid films. We use three-dimensional numerical simulations and employ a hybrid interface-tracking/level-set method, taking into account Marangoni stresses induced by gradients of interfacial surfactant concentration. Our numerical predictions for the evolution of the surfactant-free, three-dimensional wave topology are validated against the experimental work of Park & Nosoko (2003). The addition of surfactants is found to influence significantly the development of horseshoe-shaped waves. At low Marangoni numbers, we show that the wave fronts exhibit spanwise oscillations before eventually acquiring a quasi two-dimensional shape. In addition, the presence of Marangoni stresses are found to suppress the peaks of the travelling waves and preceding capillary wave structures. At high Marangoni numbers, a near complete rigidification of the interface is observed.

Domaines: Science non linéaire [physics]; Sciences de l'ingénieur [physics]; Génie des procédés

Assen Batchvarov, Lyes Kahouadji, Cristian R Constante-Amores, Gabriel Farah, Norões Gonçalves, et al.. Three-dimensional dynamics of falling films in the presence of insoluble surfactants. Journal of Fluid Mechanics, 2020, ⟨10.1017/jfm.2020.796⟩. ⟨hal-02658570⟩