Streaming by leaky surface acoustic waves
Streaming by leaky surface acoustic waves
复制标题
DOI：
10.1098/rspa.2010.0457
复制
发表时间：
2011-06-08
影响因子：
3.5
通讯作者：
Buehler, O.
中科院分区：
文献类型：
--
作者：
Vanneste, J.;Buehler, O.
声流是通过声波的耗散产生平均流，为微流体装置的抽运提供了一种很有前途的方法。近年来，几个小组一直在实验由泄漏的表面波引起的声流：（瑞利）在压电固体中激发的表面波与小体积的流体相互作用，在那里它们产生声波，由于这些波的粘性耗散，产生平均流。我们讨论了相应的拉格朗日平均流的计算，拉格朗日平均流控制着流体粒子的轨迹，从而控制了由该方法产生的流动的混合特性。该问题采用平均涡度方程来表示，该方程提取了波浪耗散和平均流耗散之间的优势平衡。特别注意在固/液界面形成的薄边界层，其中流动最好使用匹配渐近计算。这导致了滑移速度的显式表达式，其中包括边界振荡的影响。拉格朗日平均流自然地被分为三个贡献：一个内部驱动的欧拉平均流，一个边界驱动的欧拉平均流和斯托克斯漂移。尺度分析表明，后两种贡献在比声波波长大得多的器件中可以忽略，但在较小的器件中需要考虑。讨论了表面声波产生平均流的一个简单二维模型作为说明。
Acoustic streaming, the generation of mean flow by dissipating acoustic waves, provides a promising method for flow pumping in microfluidic devices. In recent years, several groups have been experimenting with acoustic streaming induced by leaky surface waves: (Rayleigh) surface waves excited in a piezoelectric solid interact with a small volume of fluid where they generate acoustic waves and, as result of the viscous dissipation of these waves, a mean flow. We discuss the computation of the corresponding Lagrangian mean flow, which controls the trajectories of fluid particles and hence the mixing properties of the flows generated by this method. The problem is formulated using the averaged vorticity equation which extracts the dominant balance between wave dissipation and mean-flow dissipation. Particular attention is paid to the thin boundary layer that forms at the solid/liquid interface, where the flow is best computed using matched asymptotics. This leads to an explicit expression for a slip velocity, which includes the effect of the oscillations of the boundary. The Lagrangian mean flow is naturally separated into three contributions: an interior-driven Eulerian mean flow, a boundary-driven Eulerian mean flow and the Stokes drift. A scale analysis indicates that the latter two contributions can be neglected in devices much larger than the acoustic wavelength but need to be taken into account in smaller devices. A simple two-dimensional model of mean flow generation by surface acoustic waves is discussed as an illustration.