Computational simulation of airflow in the human trachea-bronchial airways

Investigation of flow patterns and behaviors has become a subject of great interest in recent decades because it is a basis in the recognition of particle movement and deposition in the human respiratory tract and helps in the prediction of the effects of inhaler drugs and pollutants, and respiratory diseases such as cancer. Therefore, in this study, the effects of two boundary conditions: (1) the same flow rate in all outlets and (2) the same static pressure equal to zero in all outlets has been numerically examined in an asymmetrical model of trachea-bronchial tract. Correspondingly, the effects of the inlet flow rate changes on the flow distribution, flow patterns and the reverse flow zones were studied in the range of breathing rates 12 to 48 lit/min for a 3D non-planar model of trachea-bronchial airways consists of 4 generations. The estimation of flow distribution obtained from the second boundary condition was more accurate when compared to the real distribution in the lungs. Using the first boundary condition, the flow distribution did not change when the inlet flow rate was increased. However, for the second boundary condition, little changes revealed. The flow pattern in the lower sections was more complex than the upper sections due to the bifurcations’ curvature that causes the Dean-flow particularly when this curvature is in non-planar to the previous bifurcation. When the second boundary condition was used, the number of generated reverse flow zones was more than the other conditions and increased with increasing the inlet flow rate.