Cavitation nuclei regeneration in water-particle suspension

TL;DR

This study investigates the dynamic behavior of cavitation nuclei in water-particle suspensions under acoustic excitation, revealing a self-supporting generation process influenced by dissolved gases and particle properties.

Contribution

It introduces a novel method to monitor nuclei dynamics over many pulses and proposes a model for spontaneous nuclei generation from dissolved gases.

Findings

Stable cavitation probability emerges after thousands of pulses.

Nuclei distribution depends on particle concentration, hydrophobicity, and gas content.

Nuclei replenishment occurs through spontaneous nucleation or growth.

Abstract

Bubble nucleation in water induced by boiling, gas supersaturation or cavitation usually originates from pre-existing gas cavities trapped into solid defects. Even though the destabilization of such gas pockets, called nuclei, has been extensively studied, little is known on the nuclei dynamic. Here, nuclei of water-particle suspensions are excited by acoustic cavitation, and their dynamic is investigated by monitoring the cavitation probability over several thousand pulses. A stable and reproducible cavitation probability emerges after a few thousand pulses and depends on particle concentration, hydrophobicity, and dissolved gas content. Our observations indicate that a stable nuclei distribution is reached at a later-time, different from previously reported nuclei depletion in early-time. This apparent paradox is elucidated by varying the excitation rate, where the cavitation activity increases with the repetition period, indicating that the nuclei depletion is balanced by spontaneous nucleation or growth of nuclei. A model of this self-supporting generation of nuclei suggests an origin from dissolved gas adsorption on surfaces. The method developed can be utilized to further understand the spontaneous formation and distribution of nano-sized bubbles on heterogeneous surfaces.