Air entrainment in liquids and the resulting bubbly flow play a crucial role in mixing and oxygenation in oceans (breaking waves), rivers (waterfalls), and dam outlets. This is also vital for many industrial applications that include, among others, mixing and segregation in wastewater treatment and cooling in nuclear reactors. At the lab-scale, this complex multi-scale and multiphase problem can be investigated by employing a simple plunging liquid jet . When a plunging jet impacts a liquid pool above a threshold velocity, air enters in the form of bubbles into the bulk, through cavity formed between the surface of the jet and the free surface of the pool. This cluster of bubbles is known as bubble cloud.While previous research focused on single jets, real-world scenarios often involve large jets breaking into multiple streams, such as waterfalls. Our experiments reveal the emergence of a dome-shaped two-phase structure just beneath the surface, resulting from the interplay of shearing layers among the jets. In contrast to the bubble cloud formation observed in single injector case, this structure generates bubble cloud differently. Observations indicate that air-filled fingers eject bubbles through the end-pinching mechanism, followed by retraction.
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