Abstract
We carried out measurements on the motion of aluminum balls, which were introduced into turbulent downward duct water flow, to verify our previous prediction of the motion of a high-density ball in turbulent downward channel flow. The experimental result for the local Stokes number as a function of time was lower than that predicted. On the other hand, the experimental results for both the distance of the ball from a duct wall and the particle Reynolds number for the ball as functions of time are in agreement with those respectively predicted. These results were due to the fact that the number of tracer particles in a specific volume around the ball is not enough for the evaluation of local flow time scale, but enough for the evaluation of relative velocity between the flow in the volume and the ball.
