2006 Volume 92 Issue 10 Pages 579-583
The separation of inclusions with sizes less than several micrometers is very difficult because the flotation speed of such small inclusions is slow. Thus, increasing the volume of inclusions is essential for accelerating the removal of inclusions, and several methods for enhancing collision frequency of inclusions have been proposed hitherto. Their collision behavior, however, has not been directly observed yet. In this study, by using a water model, the collision rate of particles was quantified by directly observing the particle collision behavior in a turbulent flow. The collision rate of particles directly counted by use of image analysis was compared with a theoretical collision rate, which was calculated by substituting the turbulent energy dissipation rate obtained in a numerical analysis into the Saffman-Turner's equation. In the range with large turbulent energy dissipation rate beyond 0.06 m 2/s 3, the observed collision rates deviated above the theoretical values. In view of this, the Saffman-Turner's equation has been modified for applying to the range with the large turbulent energy dissipation rate.