Numerical Simulation of Air and Particle Transport in the Conducting Airways

Abstract

ABSTRACT

The results of numerical simulations of air and particle transport through symmetrically branching airways are summarized. These results shed light upon differences in simulated flow and particle transport behavior for (1) steady versus unsteady flow patterns, (2) two- versus three-dimensional geometries, and (3) natural versus forced user-defined entrance and exit boundary conditions. It is shown that the "steadyflow" approximation of inherently unsteady airway transport can lead to a loss of resolution of unique airflow patterns that appear to arise during the process of flow reversal. Assuming a two-dimensional geometry can result in a substantial underprediction of aerodynamic stresses, especially in the case of turbulent flows. Also, assigning entrance and exit boundary conditions can lead to the observation of gas and aerosol transport effects that do not occur during the course of natural breathing processes. It is shown that these latter effects may potentially be eliminated by extending the spatial domain under consideration, permitting identification of intrinsic airway transport properties that can be used for the study of lung transport phenomena in a macrotransport lung model. Two potential applications are discussed: (1) the use of numerical simulations to understand the role of airway morphology in the alteration of aerosol transport in diseased (versus healthy) lungs, and (2) the use of simulations for the design of aerosol particles for targeted drug delivery to the lung.