Micro-scale systems have gained considerable attention in recent years and a large amount of researches have been done in this field. In this study, the hydrodynamic interference of a droplet is comprehensively investigated under surface acoustic waves. This paper reveals the effects of some control parameters such as wave amplitude and wave frequency on the dynamical behavior of droplet. For these purposes, a two-dimensional multiple-relaxation-time color-gradient model lattice Boltzmann method is developed. This model is first validated by dynamical behaviors of a droplet subjected to shear flow. Moreover, displacement of a droplet affected by surface acoustic waves is comprehensively investigated. Our obtained simulations agree well with observations. According to our finding, the increase of frequency leads to the increment of required power to change the modes of the system from streaming to pumping or jetting states. Obtained results clearly show that hydrophobicity, reduction of viscosity, and increase of surface tension coefficient significantly influence on the flow control system and grow its sensitivity. Our results demonstrate that the minimum wave amplitude required to initiate pumping mode changes from 0.8 nm to about 1 nm when the frequency ranges are within 20 MHz to 200 MHz. The variations in jetting mode are also observed. Our findings clearly show that the minimum wave amplitude varies from about 2 nm to 4 nm when the frequency is changed from 20 MHz to 200 MHz. According to numerical analysis using lattice Boltzmann method, this work tried to capture the deformations of the fluid/fluid interface affected by surface acoustic waves and simulated the moving contact line in the high density ratio. These two main phenomena are recognized as significant parameter in our problem.

中文翻译：

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表面声波作用下平板上液滴运动的数值分析

近年来，微型系统受到了广泛的关注，并且在该领域已经进行了大量的研究。在这项研究中，全面研究了表面声波作用下液滴的水动力干扰。本文揭示了一些控制参数（如波幅和波频率）对液滴动力学行为的影响。为了这些目的，开发了二维多重松弛时间颜色梯度模型格子玻尔兹曼方法。首先通过经受剪切流的液滴的动力学行为来验证该模型。而且，全面研究了受表面声波影响的液滴的位移。我们获得的模拟结果与观察结果非常吻合。根据我们的发现，频率的增加导致所需功率的增加，以将系统的模式从流状态更改为泵送状态或喷射状态。获得的结果清楚地表明，疏水性，粘度降低和表面张力系数的增加对流量控制系统产生了显着影响，并提高了其灵敏度。我们的结果表明，当频率范围在20 MHz至200 MHz范围内时，启动泵浦模式所需的最小波幅从0.8 nm变为约1 nm。还观察到喷射模式的变化。我们的发现清楚地表明，当频率从20 MHz变为200 MHz时，最小波幅在2 nm至4 nm之间变化。根据使用格子Boltzmann方法进行的数值分析，这项工作试图捕获受表面声波影响的流体/流体界面的变形，并以高密度比模拟移动接触线。这两个主要现象被认为是我们问题中的重要参数。