Fluid dynamics in airway bifurcations: I. Primary flows

The subject of fluid dynamics within human airways is of great importance f or the risk assessment of air pollutants ( inhalation toxicology) and the t argeted delivery of inhaled pharmacologic drugs ( aerosol therapy). As cite d herein, experimental investigations of flow patterns have been performed on airway models and casts by a number of investigators. We have simulated flow patterns in human lung bifurcations and compared the results with the experimental data of Schreck ( 1972). The theoretical analyses were perform ed using a third-party software package, FIDAP, on the Cray T90 supercomput er. This effort is part of a systematic investigation where the effects of inlet conditions, Reynolds numbers, and dimensions and orientations of airw ays were addressed. This article focuses on primary flows using convective motion and isovelocity contour formats to describe fluid dynamics; subseque nt articles in this issue consider secondary currents ( Part II) and locali zed conditions ( Part III). The agreement between calculated and measured r esults, for laminar flows with either parabolic or blunt inlet conditions t o the bifurcations, was very good. To our knowledge, this work is the first to present such detailed comparisons of theoretical and experimental flow patterns in airway bifurcations. The agreement suggests that the methodolog ies can be employed to study factors affecting airflow patterns and particl e behavior in human lungs.