Inertial Deposition of Particles in the Human Upper Airway Bifurcations

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Abstract
Particle deposition in symmetric bifurcating airways due to inertial impaction was studied numerically for inspiratory flows. Three-dimensional bifurcation models were constructed. The models had different parent and daughter diameters comparable to the airway generations 3–6 of the human lung. Bifurcation angles of the models were also varied (30®, 45®, and 60®). Airflow fields in the models were obtained by a finite–element method (FIDAP, Fluid Dynamics International, Evanston, IL) for different Reynolds numbers of 100, 265, 530, and 1060 under parabolic and uniform inlet velocity conditions. The calculated flow field data were used to simulate particle trajectory in the airways. Particle deposition efficiency was obtained using the limiting trajectory method. Inlet flow velocity profile, flow Reynolds number, and bifurcation angle were found to have substantial effects on particle deposition. Based on calculated deposition results, empirical equations were derived for particle deposition efficiency as a function of nondimensional parameters of Stokes number, Reynolds number, and bifurcation angle for a parabolic or a uniform inflow. The proposed formulae compared favorably with available experimental data and are applicable to a particle lung deposition model.