Instantaneous successive particle collisions with an impeller in a stirred tank

Instantaneous successive particle collision within tens of milliseconds is visualized by the collision sound detection method. The main mechanism seems to be the discharge of a particle due to the collision against the circulation flow in the tank and the re-entrainment of the particle into the circulation flow leading to the immediate next collision. It is confirmed that the rate of instantaneous successive collisions to total successive collisions is about 22% in the examined conditions. Further, the rate is found to be practically constant in sufficiently solid-suspended conditions.