Exploiting acoustic streaming effects for microfluidic devices has been proven to be important for cell, microparticle and fluid manipulation in many fields such as, biomedical engineering, medical diagnostic devices, cell studies and chemistry. Acoustic streaming is used in acoustofluidic systems for directing and sorting microparticles as well as mixing and pumping fluids. To understand the underlying physics of such acoustofluidic systems and thus use them more efficiently in practical setups, computational modelling is critically needed. Although some work has been done to numerically model acoustofluidic systems, there are few studies to evaluate the capability and accuracy of different numerical schemes for analysing this complex multi-physics problem and to be directly validated by experiments. This paper aims to investigate the acoustic streaming effects caused by surface acoustic waves in a microchannel flow by using two different computational approaches to model the acoustic effects in three dimensions. In the first approach, we model the whole acoustic field caused by the oscillating lower wall. Here, the acoustic streaming effects were directly calculated from the density and velocity fields caused by the acoustic field. In the second approach, a low fidelity model is employed to capture the effects of acoustic streaming without modelling the acoustic field itself. In this approach, we substituted the velocity of a one-dimensional attenuating wave in the acoustic streaming force formula, and calculated the acoustic streaming force without using the density and velocity caused by the acoustic field. Both the computational methods are then validated by the results obtained from microflow experiments. The results from the second approach are in reasonable agreement with experiments while being more efficient in terms of computational cost. On the contrary, the first approach, while being computationally more expensive, allows to estimate the pressure field resulting from acoustic waves and thus predicts the dynamic behaviour of microparticles more accurately. Results suggest that the first approach is best to use for analysing the mechanism of microparticle and fluid manipulation in microfluidic devices.

已证明利用微流体设备的声流效应对许多领域的细胞、微粒和流体操作很重要，例如生物医学工程、医学诊断设备、细胞研究和化学。声流在声流体系统中用于引导和分选微粒以及混合和泵送流体。为了了解这种声流体系统的基本物理原理，从而在实际设置中更有效地使用它们，迫切需要计算建模。虽然已经做了一些工作来对声流体系统进行数值模拟，但很少有研究评估不同数值方案在分析这个复杂的多物理场问题时的能力和准确性，并通过实验直接验证。本文旨在通过使用两种不同的计算方法在三个维度上模拟声学效应，来研究表面声波在微通道流中引起的声流效应。在第一种方法中，我们对由振荡下壁引起的整个声场进行建模。在这里，声流效应直接从声场引起的密度和速度场计算出来。在第二种方法中，使用低保真模型来捕获声流的影响，而无需对声场本身进行建模。在这种方法中，我们将一维衰减波的速度代入声流力公式中，并在不使用声场引起的密度和速度的情况下计算声流力。然后通过微流实验获得的结果验证这两种计算方法。第二种方法的结果与实验合理一致，同时在计算成本方面更有效。相反，第一种方法虽然计算成本更高，但允许估计由声波产生的压力场，从而更准确地预测微粒的动态行为。结果表明，第一种方法最适合用于分析微流体装置中微粒和流体操纵的机制。第一种方法虽然计算成本更高，但可以估计声波产生的压力场，从而更准确地预测微粒的动态行为。结果表明，第一种方法最适合用于分析微流体装置中微粒和流体操纵的机制。第一种方法虽然计算成本更高，但可以估计声波产生的压力场，从而更准确地预测微粒的动态行为。结果表明，第一种方法最适合用于分析微流体装置中微粒和流体操纵的机制。