Measurement of velocity fields in a functional fluid by UVP method

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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.