Acoustic streaming can be generated around sharp structures, even when the acoustic wavelength is much larger than the vessel size. This sharp-edge streaming can be relatively intense, owing to the strongly focused inertial effect experienced by the acoustic flow near the tip. We conducted experiments with particle image velocimetry to quantify this streaming flow through the influence of liquid viscosity $\nu$ , from 1 mm ${}^2$ /s to 30 mm ${}^2$ /s, and acoustic frequency f from 500 Hz to 3500 Hz. Both quantities supposedly influence the thickness of the viscous boundary layer $\delta ={\left(\frac{\nu }{\pi f}\right)}^{1/2}$ . For all situations, the streaming flow appears as a main central jet from the tip, generating two lateral vortices beside the tip and outside the boundary layer. As a characteristic streaming velocity, the maximal velocity is located at a distance of $\delta$ from the tip, and it increases as the square of the acoustic velocity. We then provide empirical scaling laws to quantify the influence of $\nu$ and f on the streaming velocity. Globally, the streaming velocity is dramatically weakened by a higher viscosity, whereas the flow pattern and the disturbance distance remain similar regardless of viscosity. Besides viscosity, the frequency also strongly influences the maximal streaming velocity.

中文翻译：

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尖锐边缘产生的声流：液体粘度和声频的耦合影响。

即使声波波长比容器尺寸大得多，也可以在尖锐的结构周围产生声流。由于尖端附近的声流经历了强烈聚焦的惯性效应，因此这种尖锐边缘流可能会相对强烈。我们使用颗粒图像测速仪进行了实验，以通过液体粘度的影响来量化这种流动 $\nu$ ，从1毫米 ${}^2$ / s至30毫米 ${}^2$ / s，以及从500 Hz到3500 Hz的声频f。据推测这两个量都会影响粘性边界层的厚度 $\delta ={\left(\frac{\nu }{\pi F}\right)}^{\mathrm{1个}/2}$ 。在所有情况下，流动都表现为来自尖端的主要中央射流，在尖端旁边和边界层外部产生两个横向涡旋。作为特征流速度，最大速度位于 $\delta$ 从尖端开始，它随声速的平方增加。然后，我们提供经验比例定律，以量化 $\nu$ 和˚F的流速度。总体而言，较高的粘度会极大地削弱流动速度，而无论粘度如何，流型和扰动距离都保持相似。除粘度外，频率还强烈影响最大流动速度。