On quasi-steady laminar flow separation in the upper airways

Accurate prediction of the position of flow separation along a constriction is important to model fluid-structure interaction phenomena in the upper airways such as phonation and obstructive sleep apnea. Flow assumptions underlying common flow descriptions along the upper airways are formulated. Flow separation positions obtained from theories with different degrees of complexity are qualitatively and quantitatively discussed. In particular, geometrical and flow features determining the influence of viscosity are varied. Increasing the constriction degree and the constriction length is shown to affect the position of flow separation. Boundary layer solutions and simulations with the two-dimensional Navier Stokes equations result in an accurate quantitative prediction of flow separation. Furthermore, Jeffery-Hamel flow solutions qualitatively predict the effect of both constriction height and length on the position of flow separation. The ad hoc assumption applied in quasi-one-dimensional flow descriptions does not accurately predict flow separation. Copyright © 2008 John Wiley & Sons, Ltd