Shock-induced dispersion patterns of powder with diverse physical properties.

Under the strong pressure pulse induced by a shock wave, powders exhibit specific instability and dispersion patterns that develop into jets over time. We experimentally investigate how the physical properties of particles affect the dispersion of powders in both the compaction and subsequent expansion phases. Our investigation uses a laboratory-scale Hele-Shaw cell device and nano-energetic materials to generate the pressure pulse. Depending on the initial radius of the powder, distinct jetting patterns are initiated by instability in either the inner or outer boundary of the powder. The degree of particle cohesion also influences the instability, and its relationship with the morphology of the finger structure at the inner boundary is quantitatively assessed. The permeability of the powder, which depends on particle size, is another important factor determining the instability of the powder layer during the compaction phase and its inward flow in the expansion phase. Based on the experimental results, a scaling analysis is performed to identify the characteristic time scale of temporal changes in the outer boundary of the powder. The findings presented in this paper offer novel insights for improved predictions of shock-induced particle dispersion in industrial processes.