Computational fluid dynamics (CFD) simulations were carried out for an oscillatory flow in a 3D realistic model of the human central airways to reveal the effect of airway geometry on the oscillatory flow structure. This 3D realistic airway model is a computational model of multi-branching airway constructed based on X-ray CT images of actual human airways in which the airway diameter ranged from approx. 2 to 14 mm, and the flow in this airway model was simulated using CFD software (Fluent).

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... resultant inspiratory flow patterns in this 3D realistic airway model were relatively similar to patterns observed in a simplified planar multi-branching airway model, whereas the expiratory flow patterns strongly depended on the realistic airway geometry and showed more complicated secondary flow patterns. Secondary flow velocities were higher in the realistic airway model than in the simplified airway model in both the inspiratory and expiratory flows. Langrangian fluid particle tracking clarified the convective dispersion due to asymmetric inspiratory and expiratory velocity profiles.