Droplet impact dynamics on shallow pools

When a fast droplet impacts a pool of the same fluid, a thin ejecta sheet that dominates the early-time dynamics emerges within the first few microseconds. Fluid and impact properties are known to affect its evolution; we experimentally reveal that the pool depth is a critical factor too. Whilst eje...

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Bibliographic Details
Published in:Journal of fluid mechanics 2023-09, Vol.970, Article A34
Main Authors: Sykes, Thomas C., Cimpeanu, Radu, Fudge, Ben D., Castrejón-Pita, J. Rafael, Castrejón-Pita, Alfonso A.
Format: Article
Language:English
Subjects:
Direct numerical simulation
Droplets
Ejecta
Experiments
Fluid flow
Inertia
JFM Papers
Lamellae
Mathematical models
Reynolds number
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Summary:When a fast droplet impacts a pool of the same fluid, a thin ejecta sheet that dominates the early-time dynamics emerges within the first few microseconds. Fluid and impact properties are known to affect its evolution; we experimentally reveal that the pool depth is a critical factor too. Whilst ejecta sheets can remain separate and subsequently fold inwards on deeper pools, they instead develop into outward-propagating lamellae on sufficiently shallow pools, undergoing a transition that we delineate by comprehensively varying impact inertia and pool depth. Aided by matching direct numerical simulation results, we find that this transition stems from a confinement effect of the pool base on the impact-induced pressure, which stretches the ejecta sheet to restrict flow into it from the droplet on sufficiently shallow pools. This insight is also applied to elucidate the well-known transition due to Reynolds number.
ISSN:0022-1120
1469-7645
DOI:10.1017/jfm.2023.622