(6b) Drop Impact and Nucleation Under Dynamic Powder Bed Condition

Immersion type nucleation under dynamic powder bed condition is being investigated by releasing various types of liquid drops onto flowing heap of glass beads. The drop-to-particle size ratio is approximately ten. The drop impact velocity is varied by altering the release height. The shear layer depth and surface velocity of the heap flow are varied by adjusting the mass flow rate of the particles. The quantitative characterizations of the heap flow are carried out using particle image velocimetry (PIV). The details of drop impact, spreading, and nucleation are captured using a high speed video camera.

Preliminary results show that spreading behaviors of impacting drops on dynamic bed are similar to those on static bed of the same particles. However, the shapes of nuclei are more irregular in the dynamic cases. Further investigation is in progress and its results will help illustrate nucleation process in industrial granulators.