Sonoluminescence from single cavitation bubbles near solid surfaces

TL;DR

The study shows that light is emitted during bubble collapse near solid surfaces, but this light emission is not linked to surface erosion.

Contribution

This is the first observation of sonoluminescence during asymmetric bubble collapse near solid surfaces.

Findings

Light emission occurs at the most intense flow focusing sites during bubble collapse.

No correlation was found between sonoluminescence and surface erosion.

Energy focusing in bubbles and liquids follows distinct pathways.

Abstract

Sonoluminescence, the light emission from bubbles undergoing large volume oscillations, has traditionally been associated with near-spherical bubble collapses in free liquid. In contrast, highly asymmetric bubble collapses near solid boundaries are known to cause surface erosion from transient and extreme pressure build ups. While both phenomena are caused from energy focusing during bubble collapse, a connection between erosion and light emission has not been previously reported. Here, we for the first time observe the highly asymmetric toroidal cavitation bubble collapse leading to erosive effects on the nearby boundary emits light, too. Through multi-modal measurements of the bubble dynamics and the associated phenomena near solid surfaces, we find that light emission occurs exclusively at the sites and time of the most intense flow focusing. Yet, we find no correlation between the occurrence of light emission from sonoluminescence and erosion. This findings reveal that the mechanisms governing energy focusing within the bubble and in the liquid are resulting from distinct energy focusing pathways.

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