Meeting Abstract
Unidirectional flow is a respiratory condition where air flows through parts of the lung in the same direction during both inspiration and expiration. Although it was once generally thought that unidirectional airflow arose after the development of endothermy in birds, in response to increased metabolic needs, recent research has provided evidence of unidirectional airflow in crocodilians, iguanas, and varanid lizards, suggesting an alternative evolutionary history. A powerful method to explore pulmonary airflow patterns is the use of computational fluid dynamics (CFD) modeling. To gain insight into patterns of airflow in other lepidosaurs, a CFD model was developed to simulate convective airflow in the respiratory system of the bearded dragon (Pogona vitticeps) using the following methods: The anatomy was captured mathematically on a live, anaesthetized animal using computed tomography (CT). The CT scans were then visualized in Osirix. Avizo was used to segment the CT scans and generate a smoothed, high-fidelity computational mesh of the right lung. This high-fidelity computational mesh was then subjected to a series of simulations in OpenFOAM, including steady-state inhalation, steady-state exhalation, and dynamic respiration. Boundary conditions were set according to physiological data of Bearded Dragon respiration. Pressure at the outlet was set to 0 kPa and the inlet velocity was calculated based on published values of breathing frequency, inspiratory and expiratory duration, and from the following scaling relationship for tidal volume (VT) : VT = aM0.75. The mass of the specimen studied was 330 g. Inlet velocity was determined to be 5.47E-7 cm3/s. The solved simulations were visualized and processed using ParaVIEW software.
