Drop formation due to turbulent primary breakup at the free surface of plane liquid wall jets

Abstract

An experimental study of turbulent primary breakup at the free surface of plane liquid wall jets along smooth walls in still air at normal temperature and pressure is described. The study seeks a better understanding of spray formation processes in marine environments, such as in bow sheets. The measurements involved initially nonturbulent annular liquid wall jets, to approximate plane liquid wall jets, with the growth of a turbulent boundary layer along the wall initiated by a trip wire. Pulsed shadowgraphy and holography were used to observe liquid surface properties as well as drop sizes and velocities after turbulent primary breakup. Test conditions included several liquids (water, glycerol mixtures and ethyl alcohol), liquid/gas density ratios of 680–980, wall jet Reynolds numbers of 17 000–840 000 and Weber numbers of 6 100–57 000, at conditions where direct effects of liquid viscosity were small. Measurements included the following: location of the onset of surface roughness, drop size and velocity distributions after breakup, flow properties at the onset of breakup, and mean drop sizes and velocities after breakup. In general, the measurements were correlated successfully based on phenomenological theories.