Inertial Impaction and Gravitational Deposition of Aerosols in Curved Tubes and Airway Bifurcations

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Abstract
A theoretical model of the simultaneous action of inertial impaction and gravitational forces on a particle moving in three dimensional circular bends is presented. Deposition efficiencies are computed for three different idealized flow patterns: 1) uniform; 2) radially dependent, or rotational; and 3) parabolic. The bend is in a vertical plane, the inclusive angle of the bend is a variable, and its inlet can be at any angle of alignment to the horizontal. The results of these new simulations are compared with available experimental data and theoretical computations. The integral and differential distributions of deposition along the length of the tubes are examined. The relative contributions of the inertial impaction and sedimentation mechanisms to total (i.e., simultaneous) deposition are studied. The applicability of simple pipe bend models, and their appropriate limits, are examined for the deposition of aerosols in human tracheobronchial bifurcations. The conceptual model is further developed for the case in which an airway bifurcation is characterized as a contiguous system of straight and bent tubes. The results of different bifurcation simulations are compared with each other and laboratory data published in the open literature.