A long, smooth cylinder is dragged through a water surface to create a cavity with an initially cylindrical shape. This surface void then collapses due to the hydrostatic pressure, leading to a rapid and axisymmetric pinch-off in a single point. Surprisingly, the depth at which this pinch-off takes place does not follow the expected Froude1/3 power law. Instead, it displays two distinct scaling regimes separated by discrete jumps, both in experiment and in numerical simulations (employing a boundary integral code). We quantitatively explain the above behavior as a capillary wave effect. These waves are created when the top of the cylinder passes the water surface. Our work thus gives further evidence for the nonuniversality of the void collapse.
Gekle, S., van der Bos, A., Bergmann, R., van der Meer, D., & Lohse, D. (2008). Noncontinuous Froude Number Scaling for the Closure Depth of a Cylindrical Cavity. Physical review letters, 100(8), . https://doi.org/10.1103/PhysRevLett.100.084502