Synchrotron X-ray imaging of the onset of ultrasonic horn cavitation

Luc Biasiori-Poulanges; Claire Bourquard; Bratislav Lukić; Ludovic Broche; Outi Supponen

doi:10.1016/j.ultsonch.2022.106286

Synchrotron X-ray imaging of the onset of ultrasonic horn cavitation

Ultrason Sonochem. 2023 Jan:92:106286. doi: 10.1016/j.ultsonch.2022.106286. Epub 2022 Dec 30.

Authors

Luc Biasiori-Poulanges¹, Claire Bourquard², Bratislav Lukić³, Ludovic Broche³, Outi Supponen⁴

Affiliations

¹ Institute of Fluid Dynamics, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, Zurich 8092, Switzerland. Electronic address: lbiasiori@ethz.ch.
² Institute of Fluid Dynamics, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, Zurich 8092, Switzerland; Silicon Austria Labs GmbH, Villach A-9524, Austria.
³ European Synchrotron Radiation Facility, CS 40220, Grenoble F-38043, France.
⁴ Institute of Fluid Dynamics, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, Zurich 8092, Switzerland. Electronic address: outis@ethz.ch.

Abstract

High-power ultrasonic horns operating at low frequency are known to generate a cone-shaped cavitation bubble cloud beneath them. The exact physical processes resulting in the conical structure are still unclear mainly due to challenges associated with their visualization. Herein, we address the onset of the cavitation cloud by exploiting high-speed X-ray phase contrast imaging. It reveals that the cone formation is not immediate but results from a three-step phenomenology: (i) inception and oscillation of single bubbles, (ii) individual cloud formation under splitting or lens effects, and (iii) cloud merging leading to the formation of a bubble layer and, eventually, to the cone structure due to the radial pressure gradient on the horn tip.

Keywords: Cavitation; Sonication; Ultrasonic; X-ray imaging.

MeSH terms

Synchrotrons*
Ultrasonics* / methods
X-Rays