Landau Institute for Theoretical Physics of the Russian Academy of Sciences, 142432 Akademica Semenova av. 1-A, Chernogolovka, Russia.
Shubnikov Institute of Crystallography of Federal Scientific Research Center "Crystallography and Photonics" of the Russian Academy of Sciences, 119333 Leninsky pr. 59, Moscow, Russia.
Phys Rev E. 2017 Jan;95(1-1):012707. doi: 10.1103/PhysRevE.95.012707. Epub 2017 Jan 24.
We study horizontal streaming excited by means of a low-frequency and low-intensity acoustic wave in 2D freely suspended films of thermotropic smectic liquid crystals. Acoustic pressure induces fast periodic transverse oscillations of the film, which produce in-plane stationary couples of vortices slowly rotating in opposite directions owing to hydrodynamic nonlinearity. The parameters of the vortices are measured using a new method, based on tracking solidlike disk-shaped islands. The horizontal motion occurs only when the amplitude of the acoustic pressure exceeds the threshold value, which can be explained by Bingham-like behavior of the smectic film. The measurements above threshold are in good agreement with existing theoretical predictions. We demonstrate experimentally that in-plane flow is well controlled by changing the acoustic pressure, excitation frequency, and geometry of the film. The observations open the way to using the phenomenon in nondisplay applications.
我们研究了低频、低强度声波在二维自由悬浮热致向列相液晶膜中激发的横向流动。声波压力会引起膜的快速周期性横向振动，由于流体动力非线性，这种振动会产生在平面内缓慢旋转方向相反的涡旋对。我们使用一种新的方法来测量涡旋的参数，该方法基于跟踪固态盘状岛屿。只有当声压的振幅超过阈值时，才会发生水平运动，这可以用向列相膜的宾汉类似行为来解释。高于阈值的测量结果与现有的理论预测非常吻合。我们通过改变声压、激励频率和膜的几何形状实验证明了平面内流动可以得到很好的控制。这些观察结果为在非显示应用中利用这一现象开辟了道路。
