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TECHNICAL PAPERS

Numerical Modeling of Steady Inspiratory Airflow Through a Three-Generation Model of the Human Central Airways

[+] Author and Article Information
F. Wilquem

Service de Mécanique des Fluides, Machines à Fluides, Machines Thermiques, Faculté Polytechnique de Mons, Rue de Houdain, 9, 7000 Mons, Belgium

G. Degrez

Aeronautics/Aerospace Department, von Karman Institute for Fluid Dynamics, Chaussée de Waterloo, 72, 1640 Rhode St Genèse, Belgium

J Biomech Eng 119(1), 59-65 (Feb 01, 1997) (7 pages) doi:10.1115/1.2796065 History: Received March 18, 1995; Revised April 18, 1996; Online October 30, 2007

Abstract

Two-dimensional steady inspiratory airflow through a three-generation model of the human central airways is numerically investigated, with dimensions corresponding to those encountered in the fifth to seventh generations of the Weibel’s model. Wall curvatures are added at the outer walls of the junctions for physiological purposes. Computations are carried out for Reynolds numbers in the mother branch ranging from 200 to 1200, which correspond to mouth air breathing at flow rates ranging from 0.27 to 1.63 liters per second. The difficulty of generating grids in a so complex configuration is overcome using a nonoverlapping multiblock technique. Simulations demonstrate the existence of separation regions whose number, location, and size strongly depend on the Reynolds number. Consequently, four different flow configurations are detected. Velocity profiles downstream of the bifurcations are shown to be highly skewed, thus leading to an important unbalance in the flow distribution between the medial and lateral branches of the model. These results confirm the observations of Snyder et al. and Tsuda et al. and suggest that a resistance model of flow partitioning based on Kirchhoff’s laws is inadequate to simulate the flow behavior accurately within the airways. When plotted in a Moody diagram, airway resistance throughout the model is shown to fit with a linear relation of slope −0.61. This is qualitatively in good agreement with the experimental investigations of Pedley et al. and Slutsky et al.

Copyright © 1997 by The American Society of Mechanical Engineers
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