Meniscus dynamics in bubble formation. Part I: Experiment

Subsequent formation of bubbles from a single orifice on a transparent perforated plate above a gas plenum was investigated experimentally, in a laboratory column. The individual bubbles were produced in the 'bubbling mode' where the meniscus closes the orifice after each bubble detachment. The gas input was the main control parameter. The following information was obtained: gas pressure in the plenum below the plate, acoustic pressure in the liquid above the plate, and a high-speed video record of the meniscus motion inside the orifice, drilled in the plate. The meniscus behaviour was analysed and it was found that the meniscus oscillations strongly affect the subsequent bubble cycle. They are also responsible for an interesting hysteresis phenomenon. The hysteresis causes a dispersion of the bubble sizes and the bubble formation frequencies, at otherwise fixed parameters. The reason for this is seen in a strong nonlinear coupling between the final state of one cycle and the initial conditions of the next cycle. This subject is further investigated theoretically in the following contribution, see Part II.