Full-Scale DEM Simulation of Coupled Fluid and Dry-Coated Particle Flow in Swirl-Based Dry Powder Inhalers

Fine particle lift and aerodispersion are utilized as specialized technology in pharmaceutical devices such as dry powder inhalers (DPIs), where the active pharmaceutical ingredient (API) powder is delivered to the patient lungs after being dispersed and aerosolized. These processes result from the complex interplay between adhesive, impact, and hydrodynamic forces at the individual particle level. In this study, we use computational fluid dynamics–discrete element method (DEM) simulations to characterize the coupled flow field of air and API-coated carrier particles in a swirl-based DPI geometry. For the first time, the motion of particles is tracked down to the level of 10 μm API particles, whose size ratio with the carrier is 15–20 and poses serious challenges for DEM application across the full range of scales. The predicting capability with the transiently developing swirling air flow is checked first. Then, the trajectories and velocity profiles of the particles are investigated in carrier-only systems, quantifying flow patterns, local solid distribution, and expulsion rate. The dry-coated particle deaggregation is finally analyzed during inhalation, quantifying the proportion of the detached API and expulsion patterns, also in light of the local force balances, providing valuable insights into the microscopic mechanisms.