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Highlights • Our study provides the first quantitative and qualitative overview of the events following submerged injection of gas into a thin quiescent liquid sheet with a thickness of a few millimeters. • For the experimentally available range, three different flow regimes are identified and, particularly, we build a phase diagram outlining these regimes in terms of the Weber number and Bond number. • We investigated the complete evolution of periodic bubbling-bursting behavior systematically. The bubbling characteristics, which show great differences with traditional bubbling in deep liquid, are depicted and analyzed. • Using dimensional arguments, we proposed a scaling law for the rupture radius of bubbles which brings out the effects of gravity and inertia. • Focusing on the subsequent liquid jet dynamics, we unravel experimentally the intricate roles of capillary wave velocities, cavity morphology, liquid thickness and gas momentum in bubble collapse. • Our results and conclusions herein provide a new method for the control of the bursting-bubble jet and an important supplement to the physical problem of submerged gas injection. Abstract Submerged injection of gas into a thin liquid sheet is frequently observed in industrial processes. Most studies on submerged gas injection, however, focus on the phenomena happened in deep liquid pool. Few studies have been devoted to a thin liquid layer with a thickness of a few millimeters. Here, we study submerged injection of gas into a thin liquid sheet, where we quantify the behaviors of bubbling/collapse and the resulting liquid jet with a high-speed video system. For the experimentally available range of liquid depths and gas velocities, three different flow regimes are identified and we build a phase diagram outlining these regimes in terms of the Weber number and Bond number. Particularly, the complete evolution of periodic bubbling-bursting behavior is investigated systematically. The bubbling characteristics, which show great differences with traditional bubbling in deep liquid, are depicted and analyzed. Using dimensional arguments, we propose a scaling law for the rupture radius of bubbles which brings out the effects of gravity and inertia. Focusing on the subsequent liquid jet dynamics, we unravel experimentally the intricate roles of capillary wave velocities, cavity morphology, liquid thickness and gas momentum in bubble collapse. With increase of the liquid sheet thickness, jets first become fat and small and then ends up thinner, detaching more and smaller droplets due to Rayleigh-Plateau instability. Our study firstly provides the quantitative overview of the events following submerged gas injection into thin quiescent liquid and provide guides for the control of the bursting-bubble jet. [ABSTRACT FROM AUTHOR]

Discontinuous contact line pinning phenomenon appears when liquid wets discontinuous sharp features. It provides additional resistance to the gas-liquid interface and sometimes can be used as an effective approach for liquid control, such as avoiding liquid leakage by extraction holes in immersion lithography and other microfluidic devices. The discontinuous pinning effect by a hole row to the gas-liquid interface in a parallel gap was investigated in this study. We designed an experiment to investigate the behavior and the maximum resistance pressure of a hole row blocking the air-water interface in the gap. It was observed that the interface was partially pinned by the hole edges, while the unpinned parts was also stopped by the interface stretching. The pinning effect caused the interface distorted and produced additive Laplace pressure to resist the water pressure. Three failure types of the discontinuous pinning system were found, which were related to not only the hole edge pinning effect, but also the shape and position of the contact line. By analyzing the experimental results, analytical models based on the Laplace equation were built to formulate the pinning effects in the paper. The resistance pressure can be determined dependent on the developed analytical method. The experimental results agreed with the models in the failure types and maximum resistance pressure estimations. [ABSTRACT FROM AUTHOR]

Submerged gas-liquid mixture injection into water through a micro-channel shows unique fluid characteristics by various flow regimes in the micro-channel generating special jetting phenomena which have never been systematically studied. We injected air-water mixtures into water through submerged 1.0 and 1.5 mm diameter micro-channels. Bubbly, Taylor, bubble-train Taylor, churn and Taylor-annular flows were observed, and generated respective jetting flow regimes. Overall, two flow regimes namely “unstretched bubbles” and “stretched bubbles” were identified in the jet region. The former consists of three flow patterns, namely discrete bubbles, gathered bubbles and grown irregular bubbles. The latter occured when liquid slugs having strong enough momentum to stretch the bubble interface, from which single-bubble stretched, twin-bubbles stretched and even bubble rupture were further identified. We compared flow regime maps in micro-channels with those of submerged jets, and proposed the correspondence relationship, whose universality was confirmed by the consistency for different sized micro-channels. Transitions between two overall flow regimes of submerged jets, as well as flow patterns of unstretched bubbles were found determined by flow regime transitions in the micro-channel. Besides, transition laws between flow patterns of stretched bubbles were affected by the uniformity of slug length throughout the micro-channel, which were quantitatively analyzed. [ABSTRACT FROM AUTHOR]

• A new gas-liquid interface jet was observed during a suspended liquid suck process. • The jet is developed from a pressure-driven flow and maintained by coaxial gas flow. • The gas superficial velocities almost don't influence the jet spout below the nozzle. • The shear force generated by gas flow cause interface instabilities inside the tube. In the tubular co-flowing gas-liquid jet, liquid is sucked through a nozzle suspended above the flat gas-liquid interface. The liquid hump can be induced by the sudden pressure change just beneath the nozzle entrance. At a sufficiently fast initial gas superficial velocity, the interface undergoes a transition and liquid starts to be sucked. The suction flow is in the form of an axisymmetric liquid jet surrounded by an upwards coaxial gas flow. In the present study, we discuss the evolution and characteristics of the suspended liquid suction flow. The jet dynamics include the interface deformation and development (the hump stage), the tubular co-flowing jet (the spout state) and the destabilization of the liquid jet (the jet state). Tube inner diameter, suspension height, and initial gas superficial velocity are three important parameters that influence the suction flow. Due to the inward gas flow, a relatively large amount of pressure gradients is imparted to a small mass of liquid near a free surface, which leads to interface deformation. The lateral boundary of the liquid hump circumferentially shrinks and the top liquid gradually rises following the shrinkage. There is a comparatively stable axisymmetric liquid jet surrounded by an upwards coaxial gas flow inside the tube. Surprisingly, no evidence is shown the dependence of jet spout with initial gas axisymmetric superficial velocity below the nozzle through plenty of experiment figures and statistical analysis. On the other hand, the velocity difference between the fast light gas flow and the slow dense liquid is critical to the destabilization of the liquid jet. [ABSTRACT FROM AUTHOR]