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arXiv · 2602.14118

Droplet impact on surfactant-laden thin liquid films: Vortex ring dynamics

Hatim Ennayar·Hyoungsoo Kim·Jeanette Hussong
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Abstract

Droplet impact on surfactant-laden thin liquid films is investigated experimentally with emphasis on vortex ring dynamics. Bottom- and side-view imaging reveal that increasing surfactant concentration progressively stabilize vortex rings, suppress azimuthal instabilities and promote concentric mixing patterns. A regime map is established in terms of film thickness, Reynolds number, and surface-tension ratio, yielding an empirical instability threshold. Shadowgraphy observations suggest that Marangoni stresses modify early capillary-wave dynamics, potentially altering vortex ring formation and delaying instability onset. These findings clarify the link between interfacial stresses, vortex ring dynamics, and mixing patterns in thin-film droplet impact.

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Hatim Ennayar, Hyoungsoo Kim, Jeanette Hussong. 2026-02-15. Droplet impact on surfactant-laden thin liquid films: Vortex ring dynamics. https://arxiv.org/abs/2602.14118

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