Numerical study on cavitation bubble dynamics with dual-frequency excitation in magnesium alloy melt

Abstract

The enhancement and control of acoustic cavitation in liquids by dual-frequency excitation have been verified. However, the effect of the acoustic parameters of the dual sources on the cavitation bubble dynamics is not clear and further studies are needed. In this work, a dual-frequency driven bubble dynamics model is developed based on the Keller-Miksis equation. The effects of equilibrium radius, driving frequency, and acoustic pressure on the dynamic evolution of a single bubble are investigated. The results indicate that the cavitation bubble collapse strength is high and sensitive to frequency variation in the low-low or low-high frequency domain. At low-low frequency coupling, dual-frequency ultrasound enhances cavitation. At low-high frequency coupling, dual-frequency ultrasound weakens the acoustic cavitation. With both driving frequencies larger than 100 kHz, the collapse strength reduces to a stable low level and no longer responds significantly to frequency variation. Increasing the acoustic pressure enhances the synergistic effect between the two distinct frequencies. The collapse strength for two equal frequencies is independent of the pressure ratio. For two distinct frequencies, increasing the pressure ratio of a lower frequency increases the collapse strength significantly. Higher collapse strength is often obtained at the cost of longer collapse time.