Motions of a Free-Falling Sphere in the Acceleration Range in Water/Fine-Solid-Particle Suspensions.

The velocity of a free-falling sphere in the acceleration range in water/fine-solid particles has been measured by means of four ultrasonic transducers. Carbon black suspensions in the concentration range Cw=0.3∼0.5wt%, and in SiO2 suspensions of Cw=0.5∼1.0wt% were tested in this experiment. Six spheres between 7.93mm and 12.70mm were tested. From the comparison of the experimental results with the calculated results of the general equation of motion considering the Basset term, it was shown that the drag reduction occurs in carbon black suspensions.