Complex Drop Impact Morphology

The aim of this work is to understand the changes in the observed phenomena during particle-laden drop impact. The impact of millimeter-size drops was investigated onto hydrophilic (glass) and hydrophobic (polycarbonate) substrates. The drops were dispersions of water and spherical and nearly iso-dense hydrophobic particles with diameters of 200 and 500 mu m. The impact was studied by side and bottom view images in the range 150 <= We <= 750 and 7100 <= Re <= 16400. The particles suppressed the appearance of singular jetting and drop partial rebound but promoted splashing, receding breakup, and rupture. The drops with 200 mu m particles spread in two phases: fast and slow, caused by inertial and capillary forces, respectively. Also, the increase in volume fraction of 200 mu m particle led to a linear decrease in the maximum spreading factor caused by the inertia force on both hydrophilic and hydrophobic substrates. The explanation of this reduction was argued to be the result of energy dissipation through frictional losses between particles and the substrate.