AeroSolved: Multispecies aerosol evolution in the upper airways under puff–hold–inhalation profiles

This study presents an advanced evolving aerosol modeling approach that captures complex aerosol dynamics, such as polydisperse particle drift, hygroscopic growth, multispecies phase change, and wall deposition within a realistic three-dimensional airway geometry using the computational fluid dynamics code AeroSolved. Specialized boundary conditions were employed to simulate evaporation and condensation processes occurring at the air–mucus interface. The model is applied to a typical transient puff-hold-inhale scenario involving a multispecies aerosol. Simulations reveal that particles undergo significant hygroscopic growth, enhancing deposition via gravitational and inertial effects as sedimentation during the hold phase remains the dominant deposition mechanism. Notably, the study demonstrates that vapor-phase transfer, particularly for evaporative species, contributes more significantly to deposition than the particulate phase in the upper respiratory tract. Presented parametric studies explore mesh resolution sensitivity, challenge modeling assumptions, and examine wall saturation effects. Results show strong interspecies coupling and highlight the need for evolving aerosol models that account for dynamic changes in particle mixture composition. Variations in wall saturation fraction influence species evaporation and condensation dynamics, with hygroscopic growth acting as a regulatory mechanism and impacting aerosol dosimetry. Overall, this work underscores the importance of resolving multispecies interactions and evolving aerosol behavior in transient respiratory flows. It provides a foundation for future simulations involving more complex geometries, realistic breathing patterns, and chemically detailed aerosol compositions relevant to exposure assessment and toxicological risk assessment.