Gravitational oscillations of a liquid column in a pipe

Abstract : We report gravity oscillations of a liquid column partially immersed in a bath of liquid. We stress some peculiarities of this system, namely i the fact that the mass of this oscillator constantly changes with time; ii the singular character of the beginning of the rise, for which the mass of the oscillator is zero; iii the sources of dissipation in this system, which is found to be dominated at low viscosity by the entrance or exit effects, leading to a long-range damping of the oscillations. We conclude with some qualitative descriptions of a second-order phenomenon, which is the eruption of a jet at the beginning of the rise.