Shanxi Key Laboratory of Advanced Manufacturing Technology, North University of China, Taiyuan 030051, China.
Shanxi Key Laboratory of Advanced Manufacturing Technology, North University of China, Taiyuan 030051, China.
Ultrason Sonochem. 2019 Dec;59:104744. doi: 10.1016/j.ultsonch.2019.104744. Epub 2019 Aug 22.
Ultrasonic cavitation is a physical dynamic phenomenon of bubbles inflation, compression, and collapse in liquid. A dual-frequency ultrasonic cavitation dynamics model is established in this paper to investigate dynamic evolution of bubble under single and dual frequency ultrasonic modes. The variation of bubble radius, pressure, energy, temperature, and number of water vapor molecules inside the bubble in single and dual frequency ultrasonic modes are analyzed, respectively. The results show the oscillation of cavitation bubbles is more unstable and easier to collapse in dual-frequency ultrasound field than those in single-frequency ultrasound field. With the increase of the ultrasonic frequency, cavitation effect is weakened due to the shortage of oscillation period. Under the same ultrasonic power, the maximums of bubble radius, pressure, and water vapor molecules number inside the bubble in the dual-frequency mode are larger than those in the single-frequency mode. Under the ultrasonic excited by 50 kHz + 70 kHz, the maximum bubble radius and pressure can reach 36.061 μm and 2285.9 MPa, respectively, which are much larger than 18.183 μm, 730.61 MPa at 50 kHz and 14.576 μm, 332.25 MPa at 70 kHz. The calculation results of three different frequency combinations (30 kHz + 50 kHz, 40 kHz + 60 kHz and 50 kHz + 70 kHz) indicate dual-frequency ultrasound can significantly enhance the cavitation effect.
超声空化是液体中气泡膨胀、压缩和坍塌的物理动力现象。本文建立了双频超声空化动力学模型，研究了单频和双频超声模式下气泡的动态演化。分析了单频和双频超声模式下气泡半径、压力、能量、温度和气泡内水蒸气分子数的变化。结果表明，与单频超声场相比，双频超声场中空化气泡的振荡更不稳定，更容易坍塌。随着超声频率的增加，由于振荡周期的缩短，空化效果减弱。在相同的超声功率下，双频模式下气泡半径、压力和气泡内水蒸气分子数的最大值均大于单频模式。在 50 kHz+70 kHz 激励的超声下，最大气泡半径和压力分别可达 36.061 μm 和 2285.9 MPa，远大于 50 kHz 时的 18.183 μm 和 730.61 MPa，以及 70 kHz 时的 14.576 μm 和 332.25 MPa。三种不同频率组合（30 kHz+50 kHz、40 kHz+60 kHz 和 50 kHz+70 kHz）的计算结果表明，双频超声能显著增强空化效应。
