Inertial Deposition of Particles in the Human Upper Airway Bifurcations

Particle deposition in symmetric bifurcating airways due to inertial impaction was studied numerically for inspiratory Hows. Three-dimensional bifurcation models were constructed. The models had different parent and daughter diameters comparable to the airway generations 3~ of the human lung. Bifurcation angles of the models were also varied (30°, 45°, and 60°). Airftow fields in the models were obtained by a finite-element method (FIDAP, Fluid Dynamics International, Evanston, It) for different Reynolds numbers of 100, 265, 530, and 1060 under parabolic and uniform inlet velocity conditions. The calculated How field data were used to simulate particle trajectory in the airways. Particle deposition effi. ciency was obtained using the limiting trajectory method. Inlet How velocity profile, How 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 inHow. The proposed formulae compared favorably with available experimental data and are applicable to a particle lung deposition model