An enhanced Euler-Lagrangian framework for vortex dynamics and particle transport in a human dynamic airway: Model, validation, and analysis

Numerical prediction of inhaled particle fate is challenging due to the complex effects of unsteady airflow and airway motion on particle dynamics. To address this, this work presents a validated Euler-Lagrangian framework for high-fidelity simulation of fluid-structure-particle motion. The framework integrates three key components: ( i ) an enhanced Large-eddy simulation model utilizing a regularized variational subgrid closure, which provides superior prediction of near-wall flow and alleviates the excessive dissipation of the standard subgrid-scale models; ( ii ) a stochastic model for subgrid-scale particle dispersion that reconstructs the impact of unresolved velocity fluctuations on particle trajectories across the size range of 1–11 µm; and ( iii ) a dynamic mesh technique to impose clinically derived airway wall kinematics. This framework is implemented in a novel solver, SDPMFoam, within OpenFOAM. Leveraging this validated tool, we systematically quantify the coupled effects of tidal breathing and airway wall motion on micron-particle transport and deposition. The results elucidate how the wall motion fundamentally modulates vortex structures, leading to asymmetric vortex pairing and the attenuation of bronchial vortices. A critical finding is the emergence of unexpected deposition hotspots for small particles (1 and 5 µm), where regional deposition efficiency in the distal airways is amplified by up to 85 times compared to rigid-wall simulations. Furthermore, the motion delays the peak deposition time and significantly alters the spatial distribution patterns, highlighting the critical influence of inhalation timing and phase. The findings not only challenge the conventional rigid-wall paradigm but also provide a powerful, open-source tool for the broader computational physics community.