Self-Organization of Laser Induced Bubbles under the Influence of Strong Acoustic Fields in Phosphoric Acid
* Präsentierender Autor
Zusammenfassung:The mutual interaction and structure formation of cavitation bubbles in strong sound fields is still not fully understood. Here, we analyse the temporal evolution of an ensemble of bubbles seeded by a laser pulse in concentrated phosphoric acid and driven by an ultrasonic standing wave field. The bubbles nucleate at random positions in a cylindrical volume around the laser focus and immediately start volume oscillations, translations and interactions. High-speed videos show self-organization into several small spherical clusters that are driven away from the acoustic pressure anti-node, similar to single bubbles, and producing a streamer. Different bubble sizes and cylinder radii were explored by changing the laser pulse energy and the beam focusing. The temporal evolution of relevant parameters like average maximum bubble radius or void fraction is extracted from the images and discussed for the different experimental scenarios. The role of shape instabilities and the principal forces affecting both the individual and collective behaviour of the bubbles is analysed by comparing the experimental observations with a series of numerical simulations.