title: Study of non-spherical bubble oscillations near a surface in a weak acoustic standing wave field.
abstract: The interaction of acoustically driven bubbles with a wall is important in many applications of ultrasound and cavitation, as the close boundary can severely alter the bubble dynamics. In this paper, the non-spherical surface oscillations of bubbles near a surface in a weak acoustic standing wave field are investigated experimentally and numerically. The translation, the volume, and surface mode oscillations of bubbles near a flat glass surface were observed by a high speed camera in a standing wave cell at 46.8 kHz. The model approach is based on a modified Keller-Miksis equation coupled to surface mode amplitude equations in the first order, and to the translation equations. Modifications are introduced due to the adjacent wall. It was found that a bubble's oscillation mode can change in the presence of the wall, as compared to the bubble in the bulk liquid. In particular, the wall shifts the instability pressure thresholds to smaller driving frequencies for fixed bubble equilibrium radii, or to smaller equilibrium radii for fixed excitation frequency. This can destabilize otherwise spherical bubbles, or stabilize bubbles undergoing surface oscillations in the bulk. The bubble dynamics observed in experiment demonstrated the same trend as the theoretical results.
authors.affiliation: Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Xi
authors.affiliation: Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Frederic
authors.initials: F
authors.lastname: Cegla
authors.affiliation: Christian Doppler Laboratory for Cavitation and Micro-Erosion, Drittes Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Mettin
authors.affiliation: Lam Research AG, SEZ-Strasse 1, 9050 Villach, Austria.
authors.forename: Frank
authors.initials: F
authors.lastname: Holsteyns
authors.affiliation: Lam Research AG, SEZ-Strasse 1, 9050 Villach, Austria.
authors.forename: Alexander
authors.initials: A
authors.lastname: Lippert