This study brings new experimental data on the bubble formation process with a particular focus on the behaviour of the gas-liquid interface (meniscus) inside a transparent orifice on a perforated plate. The meniscus plays an important role by coupling the gas and liquid sides. The goal was to find the effect of five important control parameters on the bubble production and the meniscus behaviour (orifice diameter, plate thickness, gas chamber size, liquid height, and liquid viscosity). The gas input was also varied. Three physical signals were taken in the measurements to extract the information needed (gas pressure in plenum, acoustic pressure in liquid, and video record of meniscus motion). Several relevant quantities were measured to characterize the bubbling process (bubbling period, active orifice time, and periods of meniscus oscillations). The data obtained show how these quantities depend on the control parameters. The recognition of the role of the meniscus dynamics in the gas dispersing process with perforated plates offers a deeper insight into this important and complicated problem.
A device for "on-demand" production of bubbles is presented. The device is based on a movable needle, through which air is injected. Bubbling is controlled by a rapid needle movement, which induces the bubble detachment. Conditions for proper function of the device include the restriction on the flow rate through the needle, sufficient needle pressure drop and adequate needle acceleration. Functionality of the device is demonstrated. Bubbling from a stationary needle is also discussed and a scaling for bubble size is proposed for the case of short needles, to which a constant flow rate is imposed through tubes of a finite volume.
The bubble breakup after collision with a vortex ring was validated as source of breakup parameters for population balance modeling. This system was chosen as a deterministic alternative to the stochastic nature of bubble breakup studies under turbulent flow. The vortex ring was characterized by combining experimental visualization and numerical simulations. Breakup frequency, mean number of daughter bubbles, and its size distribution were obtained by high‐speed camera recording of the collision process. The dependence of breakup parameters on the size of the mother bubble and Weber number was determined.
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