Influence of viscosity and impingement speed on intense hydrodynamic assist in curtain coating

J. O. Marston, M. J. H. Simmons, S. P. Decent

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    Abstract

    The onset of air entrainment for curtain coating onto a pre-wetted substrate was studied experimentally in similar parameter regimes to commercial coating [Re = rho Q/mu = O(1), We = rho Q u (c) /sigma = O(10), Ca = mu U/sigma = O(1)]. As with coating onto dry substrates, a large flow-rate dependence was observed; termed hydrodynamic assist. The influence of the impingement speed and viscosity are shown to be critical and three qualitatively different regimes of assist are identified. The interaction of the impinging curtain with the pre-existing film also led to a significant hysteretic effect throughout the flow rate-substrate speed parameter space.

    Original languageEnglish
    Pages (from-to)483-488
    Number of pages6
    JournalExperiments in Fluids
    Volume42
    Issue number3
    DOIs
    Publication statusPublished - Mar 2007

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