Meeting Abstract
Unidirectional pulmonary airflow, a condition where lung gases travel in the same direction through most of the airways and throughout the respiratory cycle, has long been of interest to comparative physiologists. Recent work has revealed a wide phylogenetic distribution of this trait, beyond the confines of Aves, to include crocodilians, green iguanas, and monitor lizards, and has raised new questions about the underlying fluid dynamical phenomena occurring in unidirectional lungs. Computational fluid dynamics, which simulates patterns of flow from prescribed boundary conditions and the laws of fluid motion, provide a powerful tool to study airflow through these complex and fascinating structures. In this study, computed tomography scans were segmented into a detailed computational mesh, representing the major and minor airways of monitor lizards, Varanidae. The surface of the computational mesh expanded and contracted to simulate lung motion during ventilation and provided the boundary conditions for flow. Simulations were carried out in open-source software on an 80-processor computing cluster. Our model yields unidirectional flow in many regions of the lung and reveals airflow patterns in chambers that are too small or are inaccessible to empirical study. Further computational modeling can be used to test hypotheses regarding unidirectional flow, such as the role of internal lung partitions and the pattern of lung motion during ventilation.
