Controlled bubble formation from an orifice through harmonic gas pressure modulation

We used acoustic pressure waves to control the bubble formation from a submerged sub-millimeter orifice. The method enables the controlled periodic formation of bubbles with a high degree of reproducibility. Therefore, we were able to generate a continuous stream of fine bubbles as small as the orifice itself. This has a high demand in many industrial applications and fundamental research at the time. Using high-speed videometry, we studied the mechanism of the bubble formation and detachment along with the effect of various parameters on the bubble size. The analysis of forces acting on a growing bubble revealed the decisive effect of the liquid inertia on the bubble detachment. Moreover, based on the experimental results, we derived new detachment criteria for the bubble departure. These criteria can be used as the boundary condition for modeling the temporal evolution of the bubble size as well as calculating the final bubble volume using the Rayleigh-Plesset equation.