Measurement of velocity fields in a functional fluid by UVP method

去年，我们进行了均匀磁场作用下磁性流体中声速的精确测量。结果表明，该模型存在传播各向异性和滞后现象。但我们还无法解释这些有趣的现象。在本研究中，我们对实验装置进行了改进，以便对1 MHz、2 MHz和4 MHz的超声波传播进行实验。超声波的传播速度随超声波的频率而变化。这种变化被认为与链状团簇的长度和波长有关。我们还对这些磁性粒子团簇进行了可视化。将图像像素划分为256色调的亮度，并通过亮度分布的标准差来评价簇的增长。

We have carried out the precise measurement of sound velocity in a magnetic fluid under a uniform magnetic field last year. It was found that anisotropy of the propagation and hysteresis existed. But we have not be able to explain these interesting phenomena. In the present study, we have improved the experimental apparatus in order to carry out some experiments for 1MHz, 2MHz and 4MHz ultrasonic wave propagation. The ultrasonic propagation velocity is changed for the frequency of the ultrasonic wave. This change is supposed to be related with the length of chain-like clusters and the wave length.We have also performed visualization of these clusters of magnetic particles. Pixels of the picture was divided into lightness of 256 tones and cluster growth was evaluated by the standard deviation of the lightness distribution.