Computational Fluid Dynamics Models of Pulmonary Airflow

Computational fluid dynamics (CFD) models are a powerful means of understanding structure-function relationships in the lungs. The members of the Farmer laboratory have been working with Dr. Brent Craven to develop CFD models for a range of different vertebrates to better understand patterns of airflow as well as to understand lung evolution.  Our approach is to generate a high fidelity computational mesh from computed tomography data using a hexahedral-dominant, unstructured, open source mesh generation utility, snappy-HexMesh, from the computational continuum mechanics library, OpenFOAM.  CFD simulation of airflow is carried out using the segregated pressure-based PIMPLE (hyrid PISO/SIMPLE) algorithm, also available in OpenFOAM, to solve the time-accurate, incompressible continuity and Navier-Stokes equations.

CFD model of airflow in the right lung of a green iguana during four consecutive phases of the respiratory cycle. A) Meshes of the lung in dorsomedail views. The lines indicate planes of section shown in B through E. . B) Flow at peak inspiration with a jet eminating laterocadaud from the ostium between the cranial and caudal chambers and a second, smaller jet eminating laterocaudad in the cranial chamber. Flow along the medial wall is craniad. During exhalation flow along this wall continues craniad.
Ventromedial view of mesh with coronal plane of section. Boxed area illustrates region of strong unidirectional flow along the medial wall. During inspiration a high-speed jet eminates laterocaudad while gases move at a lower speed craniad along the medial wall. During exhalation along this portion of the wall again flow craniad.
     
   
     

Cieri, R., Craven, B., Schachner, E., Farmer, CG.  2014.  New insight into the evolution of the vertebrate respiratory system and the discovery of unidirectional airflow in iguanan lungs. PNAS 111 (48) 17218-17223. PDF Supplemental data PDF
 

 

 

 

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Evolution of Unidirectional Pulmonary Airflow