Numerical Simulation of the Oscillatory Ventilation in Simplified Human Lung Models

Abstract

To improve the understanding of gas transport mechanisms under conditions of high-frequency oscillatory ventilation (HFOV), we performed numerical simulations of the unsteady flow in simplified airway geometries using time varying Dirichlet boundary conditions (BC) for the pressure. The flow in a generic trachea shows excellent agreement with the analytical solution for non-dimensional frequencies up to Wo = 14. Nonetheless, the computational effort increases with Wo due to a long relaxation phase and strong velocity gradients near the wall despite of relatively low Reynolds numbers.We also use the pressure BCs on multiple open outlets at a single bifurcation and a three-generation airway model, while guaranteeing mass conservation. By employing identical and slightly different pressure values at the distal bifurcation ends, flow fields are reproduced, similar to that occurring under conditions of uneven physiological behaviour of different lung regions.