Numerical Investigation of Nonlinear Oscillations and Compression-Only Behavior of a Coated Microbubble Near an Elastic Wall

Abstract

During the ultrasound imaging process, the ultrasound contrast agents (UCAs) are beating near the blood vessel wall. Therefore, the purpose of the present simulation study is to investigate the effect of the presence of an elastic wall on the radial and frequency acoustic response of a UCA microbubble oscillating in a nonlinear regime. For this reason, the numerical simulation of the dynamic behavior of a coated microbubble was performed using coding in MATLAB and a Rayleigh-Plesset equation modified by Doinikov. To study the nonlinear bubble oscillations, its compression-only behavior and the sub-harmonic nonlinear component are taken from a nonlinear shell model presented by Marmottant et al. Initially, coated bubble oscillations in two linear and nonlinear regimes were investigated for two types of shell models, and it was observed that presence of the elastic wall affects the bubble's compression-only behavior. Finally, due to the importance of the subharmonic component in the nonlinear oscillation of the coated bubble, the threshold of the appearance of subharmonic components for a coated bubble near an elastic wall was investigated using the Fast Fourier Transform (FFT) and compared with the oscillation in the infinite fluid.