Upstream motion of oil droplets in co-axial Ouzo flow due to Marangoni forces
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arXiv
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| Format: | Preprint |
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2025
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| author | Bisswanger, Steffen Rocha, Duarte Dehe, Sebastian Diddens, Christian Baier, Tobias Lohse, Detlef Hardt, Steffen |
| author_facet | Bisswanger, Steffen Rocha, Duarte Dehe, Sebastian Diddens, Christian Baier, Tobias Lohse, Detlef Hardt, Steffen |
| contents | To explore the physicochemical hydrodynamics of phase-separating ternary liquids (Ouzo-type), a binary oil-ethanol mixture is introduced into a co-flowing stream of water. Oil droplets nucleate at the interface between the two liquids, leading to a larger oil droplet interacting with the ethanol-rich jet. Although buoyancy forces and hydrodynamic drag forces push the droplet in downstream direction, we observe an upstream motion. Using computational fluid dynamics simulations of a simplified model system, we identify the nucleation zone for oil droplets and uncover Marangoni forces to be responsible for the upstream motion of the droplet. A semi-analytical model allows us to identify the key parameters governing this effect. A general conclusion is that Marangoni stresses can reverse the motion of droplets through channels, where the surrounding liquid is a multi-component mixture. The insights from this work are not only relevant for channel flow, but more generally, for the physicochemical hydrodynamics of multiphase, multi-component systems. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_15716 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Upstream motion of oil droplets in co-axial Ouzo flow due to Marangoni forces Bisswanger, Steffen Rocha, Duarte Dehe, Sebastian Diddens, Christian Baier, Tobias Lohse, Detlef Hardt, Steffen Fluid Dynamics 76T30 To explore the physicochemical hydrodynamics of phase-separating ternary liquids (Ouzo-type), a binary oil-ethanol mixture is introduced into a co-flowing stream of water. Oil droplets nucleate at the interface between the two liquids, leading to a larger oil droplet interacting with the ethanol-rich jet. Although buoyancy forces and hydrodynamic drag forces push the droplet in downstream direction, we observe an upstream motion. Using computational fluid dynamics simulations of a simplified model system, we identify the nucleation zone for oil droplets and uncover Marangoni forces to be responsible for the upstream motion of the droplet. A semi-analytical model allows us to identify the key parameters governing this effect. A general conclusion is that Marangoni stresses can reverse the motion of droplets through channels, where the surrounding liquid is a multi-component mixture. The insights from this work are not only relevant for channel flow, but more generally, for the physicochemical hydrodynamics of multiphase, multi-component systems. |
| title | Upstream motion of oil droplets in co-axial Ouzo flow due to Marangoni forces |
| topic | Fluid Dynamics 76T30 |
| url | https://arxiv.org/abs/2509.15716 |