Lack of Self-Similarity in the Collapse of a Giant Bubble

Self--similarity has been the paradigmatical picture for the pinch--off of a drop. Here we will show through high-- speed imaging and Boundary Integral simulations that the inverse problem, the pinch-off of an air bubble in water, is not self- similar: A disk is quickly pulled through a surface leading to a giant, cylindrical cavity which after collapse creates an upward and a downward jet. The minimal void radius scales only in the limiting case of large Froude number like $R(t)$ $\sim$ t$^{\frac{1}{2}}$, as expected for the purely inertial regime. The collapse slows down however for lower values of Froude due to a flow component in the vertical direction introducing a second time--dependent length--scale, the curvature of the void.