Cavitation Clusters in Lipid Systems: The Generation of a Bifurcated Streamer and the Dual Collapse of a Bubble Cluster

Abstract

Several studies have reported the use of high intensity ultrasound (HIU) to induce the crystallization of lipids. The effect that HIU has on lipid crystallization is usually attributed to the generation of cavities but acoustic cavitation has never been fully explored in lipids. The dynamics of a particular cavitation cluster next to a piston like emitter (PLE) in an oil, was investigated in this study. The lipid systems, which are important in food processing, are studied with high-speed camera imaging, laser scattering and acoustic pressure measurements. A sequence of stable clusters were noted. In addition, a bifurcated streamer was detected which exists within a sequence of clusters. This is shown to originate from two clusters on the PLE tip oscillating with a 180° phase shift in time with respect to one another. Finally, the collapse phase of the cluster is shown to involve a rapid (< 10 µs) two stage process. These results show that the dynamics of cluster formation and collapse is driven by HIU power levels and might have implications in lipid sonocrystallization.

Characterising the cavitation activity generated by an ultrasonic horn at varying tip-vibration amplitudes

“…In terms of subharmonic components in the spectrum of the acoustic emission signal, the progression with increased driving has been recognised for some time [29] , [30] . The dual perspective high-speed imaging and acoustic detection configuration described here, in conjunction with the spectral model for periodic shock waves [22] , [24] , confirms that the subharmonic emission components are mediated via the shock waves generated by the primary cluster collapses, at increasing m for higher input powers, §3.3.…”

Potential Effect of Cavitation on the Physical Properties of Interesterified Soybean Oil Using High‐Intensity Ultrasound: A Long‐Term Storage Study

“…This was recorded by an in-house program (Visual Studio 2010, including Measurement Studio 2012 and USB-204 DAQ card [National Instruments]). A detailed description of the experimental setup can be found in Birkin et al (2017Birkin et al ( , 2019.…”

“…The frequency of subharmonics can be defined as f/N. f indicates the frequency of the HIU and N is an integer value (Birkin et al, 2017(Birkin et al, , 2019.…”

“…7 and 8 show the hydrophone and laser scattering data obtained during HIU application at temperatures of 24 and 34 C, respectively. Previous studies (Birkin et al, 2017(Birkin et al, , 2019 showed that during sonication a cluster of bubbles is formed closed to the tip with a streamer of bubbles that move away from the tip are generated. Cavitation clusters forming and collapsing at various periodicities in oil systems were studied and results showed that these clusters oscillate at a specific frequency and periodicity depending on the levels of HIU amplitude (power level).…”

“…Cavitation itself involves the formation, motion, and collapse of bubbles while exposed to suitable pressure changes (e.g., the ultrasonic waves), resulting in shockwave emission and high localized temperatures (particularly in the gas phase of the collapsing bubbles) (Barcikowski et al, 2019) that can change the physical properties in the resulting media (Abdullah and Chin, 2014;Hosseini et al, 2015;Silva et al, 2017). Cavitation and bubble dynamics have been vastly studied in aqueous systems, but fewer studies have been performed in lipid systems (Birkin et al, 2017(Birkin et al, , 2019. Previous research in our laboratory has reported the presence of bubbles in interesterified soybean oil during high-intensity sonication (Martini et al, 2012).…”