FIBER DEPOSITION IN AIRWAY BIFURCATIONS

In previous efforts mathematical models have been developed (Balashazy et al., 1990 a, b) to describe behavior of compact particles at airway bifurcations under the simultaneous action of inertial impactional and gravitational deposition mechanisms. Now, we expand the theory for the motion of fibrous particles where another deposition process, interception, may play an important role. Current U.S. EPA health effects concerns include both natural (asbestos) and manufactured (glass) airborne fibers. For the calculation of the deposition efficiency we assume that fibers are either parallel, perpendicular, or randomly oriented to their centers-of-mass trajectories relative to the entraining airflow. Deposition is computed using three different morphological configurations to characterize a bifurcation zone: (i) a single tube bend (Model I); (ii) a straight parent tube attached to two curved daughter tubes (Model II); and, (iii) three straight tubes joined together by two curved tube sections (Model III). A refinement of Model III is proposed to permit more accurate spatial descriptions of localized differential distributions of particle deposition efficiencies.