Fluid Stress Analysis During Airway Closure

A thin annular film lining the inside of a rigid tube is modeled as a liquid-lined airway in this study. Due to the capillary instability, the liquid film can form a plug and obstruct the airway once the ratio of the film thickness to tube radius, ε, is greater than a critical value ∼0.12. The dynamics of the closure process is simulated for a Newtonian viscous film with constant surface tension and a passive core gas phase. The numerical simulation employs the finite volume approach with a sharp interface method for the free surface. The computational results show that the wall shear stress and normal stress during closure can be strong enough to injure airway epithelial cells.