标题： 聚合物基声流体器件的边界层建模 显示英文标题

标题： Boundary-layer modeling of polymer-based acoustofluidic devices

摘要： 在由兆赫兹超声波换能器驱动的固体器件中嵌入的充满流体的微通道中，靠近约束壁的流体中粘性边界层的厚度通常比声波波长小3到4个数量级，比器件的最长尺寸小5个数量级。这种长度尺度的巨大跨度使得对这些器件进行直接数值模拟在计算机内存需求方面过于昂贵，因此引入了所谓的边界层模型。在这样的模型中，找到边界层场的近似解析表达式，并将其插入到剩余主体场的控制方程和边界条件中。由于主体场在边界层中不变化，可以使用得到的边界层模型对其进行数值计算，而无需解析边界层。然而，目前的边界层模型仅适用于相对较小的约束壁振幅的硬固体（例如玻璃和硅），而对于具有较大壁振幅的软固体（例如聚合物）则失效。在本工作中，我们将Bach和Bruus的边界层模型（J. Acoust. Soc. Am. 144, 766 (2018)）进行了扩展，以实现对软壁器件的准确模拟。该扩展模型通过与（1）分别在三维和二维中的微型亚毫米和较大毫米尺寸的聚合物器件的直接数值模拟进行比较，以及（2）与之前发表的实验数据进行比较来验证。 显示英文摘要

摘要： In fluid-filled microchannels embedded in solid devices and driven by MHz ultrasound transducers, the thickness of the viscous boundary layer in the fluid near the confining walls is typically 3 to 4 orders of magnitude smaller than the acoustic wavelength and 5 orders of magnitude smaller than the longest dimension of the device. This large span in length scale renders direct numerical simulations of such devices prohibitively expensive in terms of computer memory requirements, and consequently, the so-called boundary-layer models are introduced. In such models, approximate analytical expressions of the boundary-layer fields are found and inserted in the governing equations and boundary conditions for the remaining bulk fields. Since the bulk fields do not vary across the boundary layers, they can be computed numerically using the resulting boundary-layer model without resolving the boundary layers. However, current boundary-layer models are only accurate for hard solids (e.g. glass and silicon) with relatively small oscillation amplitudes of the confining wall, and they fail for soft solids (e.g. polymers) with larger wall oscillations. In this work, we extend the boundary-layer model of Bach and Bruus, J. Acoust. Soc. Am. 144, 766 (2018) to enable accurate simulation of soft-walled devices. The extended model is validated by comparing (1) with direct numerical simulations in three and two dimensions of tiny sub-mm and larger mm-sized polymer devices, respectively, and (2) with previously published experimental data.