Hydrodynamic Characterization of Harmonically Excited Falling-Films: A Detailed Experimental and Computational Study

ORAL

Abstract

We investigate the hydrodynamic characteristics of harmonically excited liquid-films flowing down a $20~\degree$ incline by simultaneous application of Particle Tracking Velocimetry and Planar Laser-Induced Fluorescence (PLIF) imaging, complemented by Direct Numerical Simulations. By simultaneously implementing the above two optical techniques, instantaneous and highly localised flow-rate data were also retrieved, based on which the effect of local film topology on the flow-field underneath the wavy interface is studied in detail. Our main result is that the instantaneous flow rate varies linearly with the instantaneous film-height, as confirmed by both experiments and simulations. Furthermore, both experimental and numerical flow-rate data are closely approximated by a simple analytical relationship, which is reported here for the first time, with only minor deviations. This relationship includes the wave speed $c$ and mean flow-rate $\overline Q$, both of which can be obtained by simple and inexpensive measurement techniques, thus allowing for spatiotemporally resolved flow-rate predictions to be made without requiring any knowledge of the full flow-field from below the wavy interface.

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Authors

  • Alexandros Charogiannis

    Imperial College London, Department of Chemical Engineering, Imperial College London

  • Fabian Denner

    Imperial College London, Department of Mechanical Engineering, Imperial College London

  • Berend van Wachem

    Imperial College, Imperial College London, Department of Mechanical Engineering, Imperial College London

  • Marc Pradas

    The Open University, Department of Mathematics and Statistics, The Open University, Department of Mathematics and Statistics, The Open University, Milton Keynes MK7 6AA, Department of Mathematics and Statistics, Open University, Milton Keynes, Department of Mathematics and Statistics, Open University, UK

  • Serafim Kalliadasis

    Complex Multiscale Systems Group, Department of Chemical Engineering, Imperial College London, Imperial College London, Department of Chemical Engineering, Imperial College London, Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK, Department of Chemical Engineering, Imperial College, London, UK, Imperial College - London, Department of Chemical Engineering, Imperial College London, London, UK

  • Christos Markides

    Imperial College London, Department of Chemical Engineering, Imperial College London