Edward Payne

Symmetric mode resonance of bubbles attached to a rigid boundary

Experimental results are compared with a theoretical analysis concerning wall effects on the symmetric mode resonance frequency of millimeter-sized air bubbles in water. An analytical model based on a linear coupled-oscillator approximation is used to describe the oscillations of the bubbles, while the method of images is used to model the effect of the wall. Three situations are considered: a single bubble, a group of two bubbles, and a group of three bubbles. The results show that bubbles attached to a rigid boundary have lower resonance frequencies compared to when they are in an infinite uniform liquid domain (referred to as free space). Both the experimental data and theoretical analysis show that the symmetric mode resonance frequency decreases with the number of bubbles but increases as the bubbles are moved apart. Discrepancies between theory and experiment can be explained by the fact that distortion effects due to buoyancy forces and surface tension were ignored. The data presented here are inte...

Dynamics of microbubbles targeted to surfaces: numerical and experimental modelling

Numerical calculations and illustrative experiments are presented on the volumetric oscillations of microbubbles on and near surfaces. There is a considerable theoretical and experimental literature on the acoustic interactions of bubbles. In the present study, the surface was represented by a mirror‐image bubble and the nonlinear frequency response calculated by integrating acoustically coupled sets of Rayleigh‐Plesset‐like equations. A significant shift was found in the peak nonlinear response frequency of a bubble targeted onto a surface. This effect is increased when other bubbles are nearby on the surface. Owing to the asymmetric influence of the surface, experimental images were dominated by shape‐mode instabilities, making optical determination of the peak nonlinear response frequency difficult. Moreover, it was found that even if bubbles are separated by only a small fraction of the sound wavelength, time delays owing to the finite speed of sound have a surprisingly significant influence. Calculat...

Nonlinear oscillations of air bubbles near and on a rigid boundary with time delay effects

A fundamental understanding of the effect of a surface on the resonance frequency of bubbles will be useful in the future development of diagnostic medical ultrasound equipment. In this paper we look at wall effects on the nonlinear resonance frequency response of air bubbles in water, continuing from an earlier paper which dealt with the linear response (E. M. B. Payne, S. Illesinghe, A. Ooi, and R. Manasseh, J. Acoust. Soc. Am. 118, 2841–2849 (2005)). Numerical results for micron‐sized bubbles near a rigid boundary are presented, showing a shift in frequency due to the boundary, and nearby bubbles, and a significant reduction in the amplitude of oscillations at resonance. Time delay effects are also included, which show a damping of the frequency response. Simulations are limited to the case where all bubbles oscillate in phase. An experimental method for measuring the resonance response of an air bubble attached to a surface is also outlined.