(512b) Particle interactions and transport problems at different scales: From dry powder inhalation to flows in fluidized beds

Flows of particulate material mediated by interstitial gas arise in nature and in many processes. They manifest inhomogeneities that can be traced to hydrodynamic instabilities and interparticle forces that arise through contact, van der Waals, electrostatic interactions, and capillary and viscous forces associated with liquid bridges between particles. Through three examples, this presentation will pose a few unresolved questions about physics at different scales. The first example deals with dry powder inhalation, where the inhaled air drives the fluidization of carrier particles decorated with active pharmaceutical ingredient (API) particles, the release of the API from the carrier particles, and transport through the mouth-throat region. The second example deals with coarse-grid simulations of gas-particle flows, where puzzling questions about the proper model form for the drag correction for non-cohesive and cohesive particles remain unresolved. The third example deals with the contact charging of particles in fluidized beds, where the observed effects of particle size and humidity on the extent of charging leave us scratching our heads.