Universal mechanism for air entrainment during liquid impact

M.H.W. Hendrix, W. Bouwhuis, D. van der Meer, D. Lohse, J.H. Snoeijer

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    49 Citations (Scopus)
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    When a millimetre-sized liquid drop approaches a deep liquid pool, both the interface of the drop and the pool deform before the drop touches the pool. The build-up of air pressure prior to coalescence is responsible for this deformation. Due to this deformation, air can be entrained at the bottom of the drop during the impact. We quantify the amount of entrained air numerically, using the boundary integral method for potential flow for the drop and the pool, coupled to viscous lubrication theory for the air film that has to be squeezed out during impact. We compare our results with various experimental data and find excellent agreement for the amount of air that is entrapped during impact onto a pool. Next, the impact of a rigid sphere onto a pool is numerically investigated and the air that is entrapped in this case also matches with available experimental data. In both cases of drop and sphere impact onto a pool the numerical air bubble volume Vb is found to be in agreement with the theoretical scaling Vb/Vdrop/sphere∼St-4/3, where St is the Stokes number. This is the same scaling as has been found for drop impact onto a solid surface in previous research. This implies a universal mechanism for air entrainment for these different impact scenarios, which has been suggested in recent experimental work, but is now further elucidated with numerical results.

    Original languageEnglish
    Pages (from-to)708-725
    Number of pages18
    JournalJournal of Fluid Mechanics
    Publication statusPublished - 1 Feb 2016


    • drops and bubbles
    • lubrication theory
    • thin films


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