Oscillation and Migration of Bubbles within Ultrasonic Field*

Abstract

The oscillation and migration of bubbles within an intensive ultrasonic field are important issues concerning acoustic cavitation in liquids. We establish a selection map of bubble oscillation mode related to initial bubble radius and driving sound pressure under 20 kHz ultrasound and analyze the individual-bubble migration induced by the combined effects of pressure gradient and acoustic streaming. Our results indicate that the pressure threshold of stable and transient cavitation decreases with the increasing initial bubble radius. At the pressure antinode, the Bjerknes force dominates the bubble migration, resulting in the large bubbles gathering toward antinode center, whereas small bubbles escape from antinode. By contrast, at the pressure node, the bubble migration is primarily controlled by acoustic streaming, which effectively weakens the bubble adhesion on the container walls, thereby enhancing the cavitation effect in the whole liquid.

Sound-mediated nucleation and growth of amyloid fibrils

“…Remarkably, the value of fibril rigidity modulus is near that of fibrils formed without US exposure, which exhibited an elastic modulus of 11.95±2.51 GPa, as indicated in our earlier publication (17). Considering that ultrasound can produce pressure fluctuations varying between 0.01 and 2.5 MPa, calculated and reported in previous studies (18), such conditions do not alter protein fibril stability and enable their elongation until a critical length is reached. An interesting parameter is the nanofibril critical length, with a maximum measured value of 1500 nm.…”

Emulsification mechanism in an ultrasonic microreactor: Influence of surface roughness and ultrasound frequency

“…Apart from the violent oscillation, the cavitation bubbles also undergo weak oscillation when their radius is smaller than the linear resonance radius [47] , [50] , [51] , [52] . On the weak oscillation of the oil-encapsulated cavitation bubbles, large droplets (typically d > 5 μm) break off from the oil layer, as can be seen in Fig.…”

Interactions of bubbles in acoustic Lichtenberg figure

“…Bubbles are subject to the combined effect of the driving acoustic field [30] , [31] , [32] , [33] and secondary radiation [34] from neighboring bubbles. In Fig.…”