Splashing and break-up of high-speed drops on wetted surfaces

The splashing during the high-speed impact of drops on wetted surfaces is a complex phenomenon that ejects an irregular, undulated, and bent liquid sheet. This sheet is intrinsically unstable and breaks up into secondary droplets after forming long liquid ligaments. We study this phenomenon using multiple high-resolution cameras and characterize its outcome for different velocity regimes. We show that multiple different periodic instabilities are responsible for the breakup of the ejected liquid. Such instabilities are present during the entire splashing process. A key finding is the transition from an almost unperturbed liquid sheet at low impact speeds to a strongly irregular, undulated, and bent liquid crown at high speeds. This transition correlates well with the Reynolds number and is reflected in the size and velocity of the ejected droplets. The size and velocity of the secondary droplets are also analyzed here to provide a more physical understanding of the breakup process. These findings contribute to a better understanding of fluid fragmentation mechanisms at high Reynolds and Weber numbers, with implications for applications ranging from inkjet printing to atmospheric physics and industrial spray processes.