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This work addresses knowledge gaps by integrating realistic airway structures, relevant physiological processes, and accurate representations of particle size distributions and the thermodynamics of evaporation and condensation. The aim is to enhance the predictive capabilities of computational fluid-particle dynamics (CFPD) models to provide a more realistic simulation of aerosol behavior within the respiratory system. This approach will demonstrate applicability through key applications such as e-cigarette vapor analysis, cannabis aerosol behavior, and soft mist inhalers (SMI), offering a more robust framework for understanding and predicting aerosol behavior in human respiratory systems, and facilitating more effective health and safety interventions.This work uses the volume of fluid to discrete phase (VOF-to-DPM) model to simulate the atomization process in the selected SMI configuration for predicting the effects of operating parameters on inhaler atomization. The comparisons across velocity, surface tension, and viscosity, along with their associated dimensionless numbers (We, Re, and Oh), demonstrate how these parameters govern aerosol atomization. In the velocity comparison, increasing We and Re with higher velocities reduces MMAD monotonically due to stronger inertial forces overcoming surface tension and viscous effects, while lower velocities yield larger droplets.
Airway simulation results reveal complex airflow dynamics and droplet transport behavior influenced by the inhaler geometry. Recirculation zones within the inhaler mouthpiece significantly impact initial velocity profiles and trajectories of aerosolized droplets, reducing their velocity before entering the throat. As airflow progresses through the tracheobronchial tree during inhalation, the flow transitions from high-velocity, recirculating patterns to smoother, laminar profiles, particularly in the peripheral airways. This design helps minimize early deposition and enhance deeper lung delivery. Although the total deposition fraction is lower than previously reported values, the emphasis on peripheral deposition remains consistent, with slight differences in particle size distribution and inhalation velocity likely accounting for the variations.
By advancing CFPD models and integrating realistic conditions, this study provides insight into aerosol dynamics within the respiratory system to support the development of more effective inhaler designs for better respiratory health outcomes.