Large-scale CFD simulations of airflow and particle deposition in lung airway

The flow fields in the small bronchial tubes are mostly laminar. However, they are quite complex mainly due to the geometrical effects of the lung airways. Asymmetry, nonplanarity and multiple generations are the main attributes of the lung airway geometry. There are total 23 generations of airways in human lung. The complexity of the airflow in the lung airway increases with an increasing number of generations. Particle deposition in bronchial tubes is strongly affected by these complex flow fields. Simulation of flow and particle deposition in multi-generational bronchial tube geometries is a major challenge because of the complexity of the geometry and size of the problem. The unsteady nature of inhale-exhale breathing cycles further complicates the problem. In this study, we simulate flows and particle deposition in an idealized lung geometry consisting of a ten-generation, nonplanar, bronchial tube model using our hybrid (finite element/finite volume), matrix free, parallel CaMEL solver. Steady-state inspiratory and unsteady flows were simulated with an inlet Reynolds number of 319. In this study, the large-scale CFD simulations for ten-generation bronchial tube model were successfully demonstrated. The particle transport was simulated using our Lagrangian based particle tracking model. The impact of unsteadiness on particle deposition was investigated by employing particle deposition efficiencies in each generation and particle destination maps. Particles were released at different inhalation times to investigate the unsteady effects. The results showed different particle deposition patterns for different particle release times. Particles released later in inhalation phase resulted in comparatively more particle deposition. The particle deposition before and after inhalation peak, which had identical inflow conditions, were observed to be significantly different due to the slight differences in strength of the vortices. Also, the results showed importance of geometry in later generations in particle deposition.