Computer Simulation of the Flow Field and Particle Deposition by Diffusion in a 3-D Human Airway Bifurcation

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Abstract
Air flow and ultrafine particle diffusion patterns within an airway bifurcation are investigated by numerically solving the corresponding full Navier-Stokes equations in a three-dimensional curvilinear coordinate system using PHOENICS flow-simulation software. Weibel's human lung morphology, airway generation I = O, was applied in the computer simulation. Computational parameters such as grid sizes, boundary condition treatments, iteration numbers, and convergence criteria have been verified by experimental data measured within the same (mathematically specified) bifurcation geometry. Velocity patterns generated by computer simulation show excellent agreement with the experimental results. Detailed velocity and particle concentration distributions are discussed. Results show that both the inlet and outlet flow boundary conditions have significant effects on the flow and concentration distribution patterns within the bifurcation. The scales of secondary flow within the daughter branches are shown be particularly sensitive to the inlet boundary condition.