Fragmentation dynamics of single agglomerate-to-wall impaction

The de-agglomeration characteristics of single agglomerate-wall impaction are examined using high-resolution shadowgraph imaging. Experiments are performed to investigate the effects of constituent particle size (D₅₀ from 3 to 7 μm) and air velocity on the individual size and velocity of de-agglomerated fragments at conditions relevant to dry powder inhalation systems. De-agglomerated fragment area and trajectories were used to differentiate between pseudo-elastic and inelastic collisions during de-agglomeration. Advanced image processing techniques have enabled provision of joint population distributions of fragment area and aspect ratio, which identify a bimodal dispersion of fragments during de-agglomeration. The bimodality is destroyed with increasing air velocity and also generally diminishes with time after impact. The experiment presented forms a platform for the detailed quantitative characterisation of de-agglomeration behaviour and can be useful towards the development and validation of related computational models for pharmaceutical dry powder inhalers.