Three-Dimensional Numerical Simulation of Airflow and Vibration Analysis for Upper Airway of Humans

Obstructive sleep apnea syndrome (OSAS) may cause apneas or hypopneas, both physically and emotionally harmful to their sufferers. It has been realized that the periodic intermittent cessations of breathing or reductions in airflow resulted from OSAS is closely related to the developed pathological change in upper airways of the patients. In this paper, the authors present numerical simulations of airflows and fluid-solid interaction analysis for human upper airways. The objective of the research is to investigate airfield characteristics of the human upper airway by means of computational fluid dynamics (CFD) and the finite element (FE) method. The authors reconstruct three-dimensional models of the upper airway from the nostril to the epiglottis based on CT scanning images collected from two clinic volunteers. Based on the reconstruction three-dimensional CFD models that precisely preserve original configuration of upper airways are created. The CFD analysis is carried out by the FE method with boundary conditions of pressure at the nostril and of velocity at the top of vocal cord. The non-slip boundary conditions are used on the interior walls of the upper airway. With the CFD results the pressure and velocity distributions in the airflow field are quantitatively determined. For fluid-solid interaction analyses, the upper airway in the vicinity of the pharyngeal cavity is meshed using the reconstructed model. The fluid-solid interactive computations are performed for the healthy person and the OSAS patient. The results show that the hypertrophy of the soft palate remarkably escalates both the pressure and the deformation levels of the upper airway and hinders the airflow in the cavity channels.