Research
A toroidal bubble rising across a liquid-liquid interface
(Main investigator: Eunseong Moon) doi:10.1017/jfm.2023.457
Bubbles of circular ring shape, namely toroidal bubbles, can be created by releasing a pulsed air jet into the water. We experimentally investigated the vertical penetration of a toroidal bubble through a horizontal liquid–liquid interface. As the toroidal bubble passes through the initial position of the liquid–liquid interface, a great amount of surrounding heavier liquid moves along with it. The volume of the surrounding heavier liquid is up to 50 times the bubble volume, much larger than the transported volume by a bubble of other shapes. Such volume gradually decreases as the toroidal bubble rises. The temporal changes in the liquid volume and ring radius were theoretically analyzed based on the momentum balance. We identified that such temporal changes are induced by forces acting on the surrounding liquid, particularly buoyancy and gravity. The liquid transport throughout the ascending of the toroidal bubble is expected to be applied in various industrial fields to enhance heat and mass transfer between two liquids.
Mitigation of cavitation erosion on a wall with an air pocket
(Main investigator: Changhwan Jang)
Cavitation bubble adjacent to a solid wall induces a bubble jet, which causes a cavitation erosion on a surface of the solid. Recently, an air pocket on a solid surface has been investigated to prevent a cavitation erosion. However, a hydrodynamic loading on a wall with an air pocket still requires further analysis. We numerically study the mitigation of hydrodynamic loading on a walll, and the interaction of an air entrapped in a pocket and a cavitation bubble.
Interaction of a bubble jet with viscoelastic solid
(Main investigator: Jihoo Moon)
Bubble jets are fast liquid jets caused by the asymmetric collapse of gas bubbles. Even a micron-sized bubble can generate a jet with the speed of a few hundred meters per second, exerting a large impulse onto a nearby structure. For this reason, bubble jets have been of great interest in various fields of engineering. Especially in biomedical applications, bubble jets can be utilized for targeted drug delivery. We numerically study the dynamics of a bubble jet interacting with a nearby viscoelastic solid in order to deepen our understanding of bubble collapse which occurs inside a human body.
Cavitation and jet formation in a liquid film
(Main investigator: Ehsan Mahravan) doi:10.1063/5.0060422
Cavitation occurs in a wide range of industrial, chemical, and biological contexts when liquid pressure drops below vapor pressure. The bubble commences to pulsate owing to the pressure difference with the surrounding liquid and undergoes nonspherical collapse if there is any boundary near it, such as a solid surface, a free surface, a particle, or even another pulsating bubble. We consider a bubble within a very thin liquid film. Cavitation in a liquid film occurs in laser-induced forward transfer (LIFT), a method that utilizes microscale cavitation bubbles for nozzle-free printing. Because of the presence of the film, the bubble dynamics are strongly affected by both a free surface and a solid boundary and differ substantially from those near a sole solid boundary.
Underwater explosion near a patterned surface
(Main investigator: Donghyun Kim)
An underwater explosion induces various responses such as shock wave propagation, formation of highly dynamic bubble, inducement of cavitation to surrounding fluid. These violent fluid responses are strongly affect the structural response during explosion process. These phenomena are researched for a long time, however there are issues not described clearly yet. Bubble dynamics related to an underwater explosion and structural responses by the bubble is our main research objective. Structures studied traditionally are usually confined to naval ships or submarines.
