“…For micrometre-sized ultrasonic bubbles in some practical applications, the key physical process is usually accompanied by an energetic collapse and a high-speed liquid jet. For instance, a large amplitude of bubble oscillation is an essential condition for emulsification (Yamamoto et al 2021); the jet impact plays a vital role in removing unwanted material layers on a surface (Ohl et al 2006a;Curtiss et al 2013). The associated Reynolds numbers are still much larger than 1.…”
Section: Experimental Set-upmentioning
confidence: 99%
“…Finally, a downward jet forms due to the faster contraction of the upper part, carrying some oil into the water through the interface (frame 4), which is a direct consequence of the lower inertia of the oil. Yamamoto et al (2021) supposed that such a bubble jet is an important mechanism in ultrasonic emulsification; however, no clear evidence was provided therein due to limitations of spatio-temporal resolutions. As shown in frame 5, a subsequent fast migration of the toroidal bubble in the rebound phase is observed.…”
Section: Bubble Initiation At the Water-oil Interfacementioning
confidence: 99%
“…Perdih, Zupanc & Dular (2019) found rich phenomena occurred near the liquid-liquid interface which was exposed to ultrasonic cavitation, including cavitation bubble oscillation near the interface, penetration of a water jet into the bulk oil phase, breakup of oil droplets, etc. Yamamoto, Matsutaka & Komarov (2021) experimentally studied the dynamics of acoustic cavitation bubbles near a gallium droplet interface. They partially demonstrated that a high-speed liquid jet from the bubble is the prime cause of liquid emulsification and a large amplitude of bubble oscillation is required to trigger a liquid jet.…”
We experimentally, numerically and theoretically investigate the nonlinear interaction between a cavitation bubble and the interface of two immiscible fluids (oil and water) on multiple time scales. The underwater electric discharge method is utilized to generate a cavitation bubble near or at the interface. Both the bubble dynamics on a short time scale and the interface evolution on a much longer time scale are recorded via high-speed photography. Two mechanisms are found to contribute to the fluid mixing in our system. First, when a bubble is initiated in the oil phase or at the interface, an inertia-dominated high-speed liquid jet generated from the collapsing bubble penetrates the water–oil interface, and consequently transports fine oil droplets into the water. The critical standoff parameter for jet penetration is found to be highly dependent on the density ratio of the two fluids. Furthermore, the pinch-off of an interface jet produced long after the bubble dynamics stage is reckoned as the second mechanism, carrying water droplets into the oil bulk. The dependence of the bubble jetting behaviours and interface jet dynamics on the governing parameters is systematically studied via experiments and boundary integral simulations. Particularly, we quantitatively demonstrate the respective roles of surface tension and viscosity in interface jet dynamics. As for a bubble initiated at the interface, an extended Rayleigh–Plesset model is proposed that well predicts the asymmetric dynamics of the bubble, which accounts for a faster contraction of the bubble top and a downward liquid jet.
“…For micrometre-sized ultrasonic bubbles in some practical applications, the key physical process is usually accompanied by an energetic collapse and a high-speed liquid jet. For instance, a large amplitude of bubble oscillation is an essential condition for emulsification (Yamamoto et al 2021); the jet impact plays a vital role in removing unwanted material layers on a surface (Ohl et al 2006a;Curtiss et al 2013). The associated Reynolds numbers are still much larger than 1.…”
Section: Experimental Set-upmentioning
confidence: 99%
“…Finally, a downward jet forms due to the faster contraction of the upper part, carrying some oil into the water through the interface (frame 4), which is a direct consequence of the lower inertia of the oil. Yamamoto et al (2021) supposed that such a bubble jet is an important mechanism in ultrasonic emulsification; however, no clear evidence was provided therein due to limitations of spatio-temporal resolutions. As shown in frame 5, a subsequent fast migration of the toroidal bubble in the rebound phase is observed.…”
Section: Bubble Initiation At the Water-oil Interfacementioning
confidence: 99%
“…Perdih, Zupanc & Dular (2019) found rich phenomena occurred near the liquid-liquid interface which was exposed to ultrasonic cavitation, including cavitation bubble oscillation near the interface, penetration of a water jet into the bulk oil phase, breakup of oil droplets, etc. Yamamoto, Matsutaka & Komarov (2021) experimentally studied the dynamics of acoustic cavitation bubbles near a gallium droplet interface. They partially demonstrated that a high-speed liquid jet from the bubble is the prime cause of liquid emulsification and a large amplitude of bubble oscillation is required to trigger a liquid jet.…”
We experimentally, numerically and theoretically investigate the nonlinear interaction between a cavitation bubble and the interface of two immiscible fluids (oil and water) on multiple time scales. The underwater electric discharge method is utilized to generate a cavitation bubble near or at the interface. Both the bubble dynamics on a short time scale and the interface evolution on a much longer time scale are recorded via high-speed photography. Two mechanisms are found to contribute to the fluid mixing in our system. First, when a bubble is initiated in the oil phase or at the interface, an inertia-dominated high-speed liquid jet generated from the collapsing bubble penetrates the water–oil interface, and consequently transports fine oil droplets into the water. The critical standoff parameter for jet penetration is found to be highly dependent on the density ratio of the two fluids. Furthermore, the pinch-off of an interface jet produced long after the bubble dynamics stage is reckoned as the second mechanism, carrying water droplets into the oil bulk. The dependence of the bubble jetting behaviours and interface jet dynamics on the governing parameters is systematically studied via experiments and boundary integral simulations. Particularly, we quantitatively demonstrate the respective roles of surface tension and viscosity in interface jet dynamics. As for a bubble initiated at the interface, an extended Rayleigh–Plesset model is proposed that well predicts the asymmetric dynamics of the bubble, which accounts for a faster contraction of the bubble top and a downward liquid jet.
“…Ultrasound irradiation in EtOH refines liquid metal and alloy into NPs. This phenomenon is caused by sonophysial effects, such as the microjet flows and shock waves associated with cavitation collapse [32] . Fig.…”
“…When the bubbles collapse, high temperature is generated in them and enormous energy is released to the surrounding liquid [5] . Cavitation has been widely used in all kinds of fields, such as sonochemistry [6] , [7] , [8] , cleaning [9] , [10] , emulsification [11] and so on. If the amplitude of driving pressure is high enough, nonlinear pulsation of bubble will emerge [12] , [13] .…”
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