A Numerical Investigation on Dynamics and Breakup of Liquid Sheet

The details on dynamics and breakup processes of liquid sheets are numerically investigated by considering two liquid sheet arrangements: the contraction of liquid sheet in a still quiescent gas medium, and a moving liquid sheet in a gas medium of much higher velocity compared with the liquid sheet. The first part of the study reveals that the surface tension forms the capillary wave on the liquid sheet surface. By extensive calculation, it is conformed that only surface tension force cannot disintegrate the liquid sheet. The dragging of liquid by co-flowing gas is very important for the occurrence of sheet breakup. To prove this concept, the second part of the investigation is performed, which reveals the details of breakup processes. Two effects are observed: the aerodynamic effect and the surface tension effect. The main function of the aerodynamic effect is to stretch the liquid sheet by drag force and create the steps on the sheet surface which is then followed by a pair of vortices and stagnation point prior to the end of every step. When the thickness of the sheet becomes thin enough, the dragging of liquid by the gas flow at the upstream of the neck part of the bulbous tip causes formation of a pair of vortices and stagnation point on the thin portion of the liquid sheet restricts the liquid flow and eventually the breakup occurs.