Numerical Investigation of the Flow-Induced Deformation in the Human Respiratory Airway

Prediction of compliant wall deformation in the respiratory airway was made numerically. An anatomically correct numerical domain comprised of the nasal cavity, pharynx, larynx and trachea was constructed using a human CT image of a male volunteer. Time dependent air flow was investigated by adopting an LES (large eddy simulation) technique to capture the unsteady nature of the flow in the respiratory airway. The analysis of uni-directional FSI (fluid structure interaction) was followed to evaluate the surface deformation. In the absence of reliable in-vivo measurement data for the mechanical properties of the inner tissues throughout the respiratory airway, the corresponding values of animals were used. While the lowest pressure was found to occur near the junction between the larynx and trachea, a larger deformation was observed in the region between the nasal cavity and trachea. In fact, the local deformation in the larynx was about 10 times larger than the local deformation detected in the nasal cavity area. The large deformation is attributed to the relatively smaller values of Young’s modulus in the larynx. The fact that the pressure change in time is well correlated with the amount of deformation with small phase lag implies the importance of accurate prediction of the unsteady flow fields.