Numerical study of cavitation threshold by use of bifrequency excitation

Previous experiments on the influence of waveform excitation on ultrasonic cavitation threshold and activity showed that the combination of two neighbouring frequency components modifies cavitation threshold and stimulates cavitation activity beyond threshold in comparison to a classical monofrequency waveform. For high monofrequency thresholds, the bifrequency excitation reduces the threshold value. For low monofrequency thresholds, the bifrequency threshold is higher, which shows that nonlinear effects are involved in the process. In-situ measurements of the amplitudes of the difference frequency component show that this low frequency is too weak to trigger cavitation alone. Numerical simulations of the dynamics of a single bubble in a bifrequency oscillating pressure field were done. They show that the bifrequency excitation modifies the cavitation threshold for specific initial bubble radius but is not sufficient to explain experimental observations. To simulate first-order nonlinear propagation effec...