Surface acoustic waves have gained much attention in flow control given the effects arising from acoustic streaming. In this study, the hydrodynamic interference of a drop under surface acoustic waves is comprehensively investigated and the contact angle hysteresis effects are considered, too. This paper reveals the effects of some control parameters such as wave amplitude and wave frequency on the dynamical behaviors of drop. For these purposes, a multiple-relaxation-time color-gradient model lattice Boltzmann method is developed. In these case studies, wave frequency and amplitude were in the ranges of 20–60 MHz and 0.5–2 nm, respectively. In addition, the density ratio of 1000, the kinematic viscosity ratio of 15, Reynolds numbers of 4–24, Capillary numbers of 0.0003–0.0008 and Weber numbers of 0–0.4 were considered. Results show that drop would not move, but would incline in the direction of wave propagation equal to radiation angle when the wave amplitude is low. However, the drop will initiate to move as wave amplitude is progressively augmented. Meanwhile, the increase in frequency leads to an increment of required power to change the modes of the system from streaming to pumping or jetting states. The obtained results clearly show that a reduction in viscosity and an increase in surface tension coefficient significantly influence the flow control system and enhance its sensitivity. Also, the contact angle hysteresis modeling can improve the numerical results by up to 20%.

中文翻译：

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接触角滞后对使用表面声波进行液滴操作的影响

考虑到声流产生的影响，表面声波在流量控制中得到了很多关注。在这项研究中，综合研究了表面声波下液滴的流体动力干扰，并考虑了接触角滞后效应。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。为此，开发了多松弛时间颜色梯度模型格子玻尔兹曼方法。在这些案例研究中，波的频率和幅度分别在 20-60 MHz 和 0.5-2 nm 的范围内。此外，密度比为 1000，运动粘度比为 15，雷诺数为 4-24，毛细管数为 0.0003-0.0008，韦伯数为 0-0.4。结果表明，当波幅较低时，水滴不会移动，但会向与辐射角相等的波传播方向倾斜。然而，随着波幅的逐渐增加，水滴将开始移动。同时，频率的增加导致将系统模式从流向泵送或喷射状态改变所需功率的增加。所得结果清楚地表明，粘度降低和表面张力系数增加显着影响流量控制系统并提高其灵敏度。此外，接触角滞后建模可以将数值结果提高多达 20%。随着波幅逐渐增加，水滴将开始移动。同时，频率的增加导致将系统模式从流向泵送或喷射状态改变所需功率的增加。所得结果清楚地表明，粘度降低和表面张力系数增加显着影响流量控制系统并提高其灵敏度。此外，接触角滞后建模可以将数值结果提高多达 20%。随着波幅逐渐增加，水滴将开始移动。同时，频率的增加导致将系统模式从流向泵送或喷射状态改变所需功率的增加。所得结果清楚地表明，粘度降低和表面张力系数增加显着影响流量控制系统并提高其灵敏度。此外，接触角滞后建模可以将数值结果提高多达 20%。所得结果清楚地表明，粘度降低和表面张力系数增加显着影响流量控制系统并提高其灵敏度。此外，接触角滞后建模可以将数值结果提高多达 20%。所得结果清楚地表明，粘度降低和表面张力系数增加显着影响流量控制系统并提高其灵敏度。此外，接触角滞后建模可以将数值结果提高多达 20%。