Abstract
The spherical stability of an acoustic cavitation bubble under dual-frequency excitation is investigated numerically. The radial dynamics is described by the Keller–Miksis equation, which is a second-order ordinary differential equation. The surface dynamics is modelled by a set of linear ordinary differential equation according to Hao and Prosperetti (1999), which takes into account the effect of vorticity by boundary layer approximation. Due to the large amount of investigated parameter combinations, the numerical computations were carried out on graphics processing units. The results showed that for bubble size between RE=2μm and 4μm, the combination of a low and a high frequency, and the combination of two close but not equal frequencies are important to prevent the bubble losing its shape stability, while reaching the chemical threshold (Rmax/RE=3) (Kalmár et al., 2020). The phase shift between harmonic components of dual-frequency excitation has no effect on the shape stability.
Highlights
In a liquid that is irradiated with high-frequency ultrasound, thou sands of micron-sized oscillating bubbles are formed
The surface dynamics is modelled by a set of linear ordinary differential equation according to Hao and Prosperetti (1999), which takes into account the effect of vorticity by boundary layer approximation
The phase shift between harmonic components has no effect on the shape stability
Summary
In a liquid that is irradiated with high-frequency ultrasound, thou sands of micron-sized oscillating bubbles are formed. For small (below 3 μm), medium (between 3 μm and 6 μm), and large bubbles (above 6 μm), the best choice of fre quency combinations are the single frequency with low value (Giant Response [19]), a mixture of low and high frequencies, and a single frequency that is near to the main resonance frequency, respectively. These observations were compared with the results of the present investigations. The obtained numerical results showed two shape stabilizing effect of the dual-frequency excitation for medium-sized bubbles. The phase shift between harmonic components has no effect on the shape stability
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