Planar liquid jet: Early deformation and atomization cascades

The temporal evolution of three-dimensional instabilities on a planar liquid sheet segment is studied using direct numerical simulation, and the level-set and volume-of-fluid methods for the liquid-gas interface tracking. Three atomization cascades are distinguished at early breakup, which are well categorized on a gasWeber number (We(g)) versus liquid Reynolds number (Re-l) map. These atomization processes include lobe stretching that occurs at low Re-l and low We(g), hole and bridge formation that occurs at moderate Re-l and high We(g), and lobe corrugation occurring at high Rel and low We(g). Qualitative comparison between the sizes of the ligaments and droplets that result from each process is presented. A transitional region between the prescribed atomization domains is found. At high Rel, the transitional boundary is a constant Ohnesorge line defined based on gas We and liquid Re (Oh(m) equivalent to root We(g)/Re-l). At low Rel, the transitional region follows a hyperbolic line on the We(g)-Re-l plot. These atomization processes are qualitatively independent of the jet geometry-seen in both planar and round liquid jets. At a constant density ratio, characteristic times for the hole formation and for the lobe and ligament stretching are different-the former depending on surface tension and the latter on liquid viscosity. In the transitional region, both characteristic times are of the same order. Published by AIP Publishing.