Bubble Breakup in Water: Memory, Oscillations, and the Vertical Direction

Using high-speed video, we have studied scaling and memory of the non-universal singularity at bubble pinch-off. We find that when initial conditions break the cylindrical symmetry of the neck of air,\footnote{N.C.~Keim et al., Phys.Rev.\ Lett.\ \textbf{97}, 144503 (2006)} the shape of its cross-section oscillates during its collapse.\footnote{L.\ Schmidt and W.W.Zhang, abstract submitted to APS DFD 2007} These oscillations determine how and when the collapse ends in a topological transition. We also report on a new experimental geometry that replaces the air bubble with a second nozzle facing the first. This geometry nearly eliminates both the vertical shape asymmetry of the neck and its upward motion during collapse, and is therefore a simpler case for theory and simulation. It also further demonstrates the independence of dynamics at different heights, and the role of initial conditions.