[Numerical study on inspiratory flows in two and three generation bronchi of human lung airways].

The main physiological function of respiratory system is exchange of oxygen and carbon dioxide between atmosphere and blood. Its physiological process is closely related with air flow and transport in respiratory airway. This paper studies numerically the inspiratory flows in a two generation and a three generation bronchial airway. The numerical results of the two generation bronchi show that the present computations fit the available experiments very well. For three generation bronchi, no separation appears within the whole airway under normal breathing rate, which is contrary to the occurrence of separation at even low Reynolds number by the previous two dimensional models. Strong secondary flow phenomenon, skew and m-shaped main flow velocity profiles are found in the airways due to geometrical curvature and bifurcation. These increase shear stress acting on the inner wall as well as on the anterior and posterior wall in the bifurcating airways. In the end bronchi of the three generation airway, the mass flow rates in medial and lateral bronchi are unequal, and the mass flow ratio between the medial and the lateral bronchi is 1.2 at the flow conditions considered.