Dual-frequency ultrasound has been widely employed to enhance and regulate acoustic droplet vaporization (ADV) but the role of ultrasonic nonlinear effects on it remains unclear. The main objective of this study is to investigate the influence of nonlinear effects on the control of ADV nucleation under different dual-frequency focused ultrasound conditions. ADV nucleation of PFC nanodroplets activated by nonlinear dual-frequency ultrasound was modeled and parametric studies were conducted to investigate the influence of dual-frequency ultrasound frequency and acoustic power on the degree of nonlinearity (DoN), nucleation rates and dimensions of the nucleation region in a wide parameter range. The results showed that the ultrasonic nonlinearity caused a significant decrease in peak negative pressure due to waveform distortion, which leads to a lower nucleation rate in the nonlinear model compared to that in the linear model. Furthermore, the distributions of nucleation regions were also affected by the interaction between waves of different frequencies and cloud-like spatial distributions were produced, which could be modulated by the dual-frequency ultrasound parameters and have great potentials in the spatial regulation of the ADV and customized treatment protocols in clinical applications. In addition, represented by 1.5 MHz + 3 MHz, such a dual-frequency combination of fundamental and second harmonic could effectively enhance ultrasonic nonlinear effects with relatively lower peak negative pressure and higher DoN. Therefore, nonlinear effect of the dual-frequency ultrasound plays an important role in the ADV regulation, which should be considered in the numerical model and practical applications.

中文翻译：

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双频聚焦超声对声液滴汽化按需调节的非线性影响

双频超声已被广泛应用于增强和调节声学液滴汽化（ADV），但超声非线性效应对其的作用仍不清楚。本研究的主要目的是研究不同双频聚焦超声条件下非线性效应对ADV成核控制的影响。对非线性双频超声激活的 PFC 纳米液滴的 ADV 成核进行了建模，并进行了参数研究，以研究双频超声频率和声功率对非线性程度 (DoN)、成核速率和成核区域尺寸的影响。参数范围宽。结果表明，超声波非线性导致波形畸变导致峰值负压显着下降，导致非线性模型中的成核率低于线性模型。此外，成核区域的分布还受到不同频率波之间相互作用的影响，产生云状空间分布，可以通过双频超声参数进行调制，在ADV和ADV的空间调控方面具有巨大的潜力。临床应用中的定制治疗方案。此外，以1.5MHz+3MHz为代表，这种基波和二次谐波的双频组合可以有效增强超声非线性效应，具有较低的峰值负压和较高的DoN。因此，双频超声的非线性效应在ADV调节中起着重要作用，在数值模型和实际应用中应予以考虑。