The pulsatile flow field in the human lung is numerically and experimentally investigated. The realistic lung geometry of a human subject was acquired down to the sixth generation of bifurcation and used as a tracheobronchial model. The numerical analysis is based on a lattice-boltzmann method which is particularly suited for flows in extremely intricate geometries such as the upper human airways. The measurements are performed via the particle-image velocimetry method in a transparent cast generated from the original dataset. Experimental and numerical results are analyzed in a comparative way and a thorough discussion of the three-dimensional flow structures emphasizes the unsteady character of the flow field. It is evidenced that the asymmetric geometry of the human lung plays a significant role for the development of the flow field in the respiratory system. Secondary vortex structures and their temporal formation are analyzed and described in detail for two respiration frequencies. It is shown that the qualitative structure of the intricate flow field does not vary if a critical mass flux rate is exceeded. at inspiration, the primary flow shows separated flow regions and is highly influenced by secondary flow structures. by contrast, at expiration the primary flow distribution is far more homogeneous with a higher level of vorticity.
The flow in a realistic model of the human lung is numerically simulated at steady and unsteady inspiration and expiration. A model of a human lung ranging from the trachea down to the sixth generation of the bronchial tree is used for the simulation. The numerical analysis is based on the Lattice-Boltzmann method, which is particularly suited for flows in extremely intricate geometries such as the upper human airways.The results for steady air flow at inspiration and expiration for a diameter based Reynolds number of Re D = 1250 evidence secondary vortex structures and air exchange mechanisms. It is shown that the asymmetric geometry of the human lung plays a significant role for the development of the flow field in the respiratory system. Secondary vortex structures observed in former studies are reproduced and described in detail.The solutions for unsteady respiration allow a detailed analysis of the temporal formation of secondary flow structures whereas the time dependence is much more pronounced at inspiration than at expiration.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.