Environmental Engineering Reference
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FIGURE 5.3  CFPD simulations of particle trajectories in a bifurcating airway using FLUENT 6.0. The low
rate is 120 L/min, and the two panels show trajectories for two different sets of initial particle locations.
in lung airways. Morphological models of these airways are discussed later in this chapter. CFPD
studies have been performed for the oral cavity, 70-72 nose, 73-77 and pharynx (throat). 78
5.3.2  M erits and  l iMitations oF  d ePosition  M odels
Each deposition model class has both scientiic strengths and drawbacks. In selecting a suitable
deposition model one must consider many factors, including the scientiic foundations of the mod-
els, the desired level of biological realism, and the available data and computing resources.
5.3.2.1  Scientiic Foundations
The scientiic foundations of the different classes of models must be considered when selecting a
model for the interpretation of experimental data or the prediction of particle deposition pattern.
Empirical models may be valid for the physical system for which they were derived, but application
to other systems may result in spurious conclusions. In addition, deterministic models are only as
valid as the assumptions made in their derivation. One must be aware of these assumptions and use
the models accordingly. Stochastic models are derived from observations of morphological vari-
ability; however, such formulations can be generated only if an appropriate amount of experimental
data is available. One must be mindful of the limitations of stochastic models derived from limited
experimental data. CFPD modeling is based on well-established methods that have been in use for
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