Contraction of infinite-long air sheet at capillary-inertial regime

Abstract

The contraction of a two-dimensional infinite-long flat air sheet in a liquid environment at a capillary-inertial regime with an Ohnesorge number Oh ⩽ 0.01 was investigated numerically. The contraction velocity first increases to a maximum and then decreases and follows a scaling U*∼t*−0.2. In this range of Oh number, pinch-off and oscillation were always observed, and two pinch-off mechanisms were identified as end-pinching (Oh ⩽ 0.006) and oscillation-induced pinch-off (Oh ⩾ 0.007), which also correspond to two oscillation regimes of the rim. Different modes of vortex shedding and merging, co-rotating, and separation of vortices are observed; the interaction between the rim and the vortices is responsible for the complicated contraction dynamics.