Water entry dynamics of hydrophobic spheres near floating debris on a deep liquid pool

We take the enduring topic of water entry further by documenting splash features generated by the impact of hydrophobic spheres with floating debris atop a deep liquid pool. Proximal interaction with floating debris is yet another means to manipulate splash dynamics. In this experimental study, we systematically investigate the fluid-structure interactions between floating debris and hydrophobic spheres for Froude numbers in the range of 21-74, and sphere-debris separation distance. Thus, we observe previously undocumented sub- and supersurface fluid interactions. Generally, hydrophobic spheres produce a radially expanding splash crown just above the free surface simultaneously with a deep seal cavity characterized by smooth cavity walls below the free surface, and a vertically-protruding Worthington jet following cavity collapse. The proximal presence of debris atop the free surface with respect to impacting spheres prohibit radial fluid expansion, yielding lopsided splash crowns, non-uniform air-entraining cavities, and in some cases, lateral sphere migration. Such observations augur well for fluid-structure interactions where splash and trajectory control are desirable.