Numerical Simulation of Ozone Uptake in the Respiratory Tract During Steady Inspiratory Flow
Banafsheh Keshavarzi, James S. Ultman, and Ali Borhan
The pattern of lung injury induced by the inhalation of ozone is believed to depend on the dose delivered to different tissues in the respiratory tract. To test this hypothesis, we performed numerical simulations of ozone transport and uptake in anatomically- correct geometries of the conductive airways of a Rhesus monkey. The airway geometry was created using three-dimensional reconstruction of the tracheobronchial tree from MRI images of the lung, and an unstructured volume mesh was generated for the first few generations of the resulting branched structure. Three dimensional numerical solutions of the Navier-Stokes, continuity, and species convection- diffusion equations were subsequently obtained for steady inspiratory flow at Reynolds number 230. The reaction model in the epithelial lining fluid was assumed as an infinitely fast reaction model. The total rate of O3 uptake within each generation was determined, and hot spots of O3 flux on the airway walls were identified. Spikes in O3 flux appeared downstream of the first bifurcation, as was true for focal sites of epithelial damage previously observed in rats . Results of the three dimensional simulations for O3 uptake along a single asymmetrically- branched airway path were also compared to the predictions of an axisymmetric single-path model (ASPM). Single-path simulations of gas uptake were in good agreement with predictions of the more realistic three-dimensional simulations.
Keywords: Axisymmetric single-path model, Ozone, Computational fluid dynamics, Lower airways