Abstract
The respiratory flow-pattern at the human oral airways was examined for various inhalation flow rates, since it is important for the inhalation therapy of oral diseases to estimate particle deposition. The airflow pattern for the inhalation flow rate of 9, 25, 50 l/min was analyzed numerically with 3-D reconstruction of the human oral airways. The human oral airways model was obtained from the images of Magnetic Resonance Imaging (MRI) analyzed by Rhinoceros, which has 3-D CAD modeling function. Numerical analysis of the airflow pattern in this human oral airways model has been performed by the thermodynamic fluid analysis code STAR-CD combined with the mesh generation function of Pro-Modeler. 52 MRI images were taken vertically at intervals of 2mm on the oral cavity, and 52 MRI images were also taken horizontally at intervals of 2mm on the pharynx and larynx, then outlines of airways were extracted. The cross-sectional data were inputted into the Rhinoceros and then arranged in Cartesian coordinate system. In those manners, the 3-D model of the human oral airway was obtained. The numerical results showed that vortex occurred near the larynx for each inhalation flow rate. Furthermore, the airflow pattern was relatively uniform in the oral cavity and the upper side of trachea. Consequently, it was suggested that the airflow pattern in the human oral airways was not changed qualitatively for the inhalation flow rate of 9, 25, 50 l/min.
