论文标题

尖锐边缘产生的声流:液体粘度和声学频率的耦合影响

Acoustic streaming generated by sharp edges: the coupled influences of liquid viscosity and acoustic frequency

论文作者

Zhang, Chuanyu, Guo, Xiaofeng, Royon, Laurent, Brunet, Philippe

论文摘要

即使声学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。这种尖锐的流媒体可以相对强烈,\ textColor {blue} {{由于尖端附近的声流所经历的强烈惯性效应。}我们进行了粒子图像速度测定量的实验,以量化这种流流通过1 mm $ $ $^2 $ $^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^$^2 $^2 mm $^$^2 mm^$^2 mm^$^2 mm^2 mm^2 mm^$^2 mm/ Hz至3500 Hz。据说这两个数量都会影响粘性边界层$δ= \ left的厚度(\fracν{πf} \ right)^{1/2} $。在所有情况下,流流从尖端出现为主要中央射流,从而在尖端和边界层外产生了两个侧向涡旋。作为特征流速度,最大速度位于距尖端$δ$的距离,它随着声速的平方而增加。然后,我们提供经验缩放法律,以量化$ν$和$ f $对流速度的影响。在全球范围内,流速度通过较高的粘度大大削弱,而流动模式和干扰距离仍然保持相似之处。除粘度外,频率还强烈影响最大流速度。

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, \textcolor{blue}{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 $ν$, 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 $δ= \left(\fracν{πf}\right)^{1/2}$. 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 $δ$ from the tip, and it increases as the square of the acoustic velocity. We then provide empirical scaling laws to quantify the influence of $ν$ 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.

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