A review on numerical studies of airflow dynamics and particle deposition in human respiratory system

Accurate assessment and prediction of airflow dynamics and particle deposition in the human respiratory tract are essential for human health, involving inhaled drugs for treating various diseases and toxic particles that can cause illnesses. This intricate process involves complex multiphase flow with distinct respiratory characteristics. Computational fluid dynamics (CFD) acts as a bridge, overcoming the limitations of in vivo and in vitro experiments and providing a means to fully comprehend and reveal the fundamental mechanisms of respiratory flow and particle behavior on a microscopic scale. This paper provides a comprehensive overview and concise summary of recent advancements in the numerical simulation of airflow and particle deposition in the human respiratory tract. Particularly, it summarizes the transition of respiratory tract models from segmented models to emerging physiological characteristic models and whole-lung airway models, and the latest developments on the effects of key factors such as geometric variations, respiratory patterns, and particle physical/chemical properties on respiratory flow and particle deposition. A notable focus of this review is on emerging physiological characteristics models and their associated complex airflow and particle dynamics inside it. The paper concludes with recommendations for future research to further advance the development of this field.