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    Drop spreading and penetration into pre-wetted powders

    Year: 2013

    Journal: Powder Technology, 239, 128-136, 20130926

    Authors: J.O. Marston, J.E. Sprittles, Y. Zhu a, E.Q. Li, I.U. Vakarelski, S.T. Thoroddsen

    Organizations: Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia, Mathematical Institute, University of Oxford, 24-29 St Giles, Oxford, OX1 3LB, UK, Clean Combustion Research Centre, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia

    We present results from an experimental study of the impact of liquid drops onto powder beds which arepre-wetted with the impacting liquid. Using high-speed video imaging, we study both the dynamics of theinitial spreading regime and drainage times once the drop has reached its maximum spread on the surface.During the initial spreading stage, we compare our experimental data to a previously developed modelwhich incorporates imbibition into the spreading dynamics and observe reasonable agreement. We findthat the maximum spread is a strong function of the moisture content in the powder bed and that thetotal time from impact to complete drainage is always shorter than that for dry powder. Our results indicatethat there is an optimum moisture content (or saturation) which leads to the fastest penetration. We usesimple scaling arguments which also identify an optimum moisture content for fastest penetration, whichagrees very well with the experimental result.