Numerical analysis of particle deposition in asymmetrical human upper airways under different inhalation cycles

It is recognised that knowledge of air flow characteristics in the tracheo-bronchial tree is essential to the understanding of airway resistance, intrapulmonary gas mixing and deposition of airborne particles. Numerical and mathematical methods have previously been used extensively to obtain particle deposition patterns inside a single airway and various regions of the human lung for a range of physiological conditions. However, detailed analysis of particle deposition, in asymmetrical human upper airways, under transient conditions, has not been uncovered in published literature at the time this research commenced. In this research study, a commercial CFD package, called "CFX Workbench 11" was deployed to analyse flow fields, transient flow and particle deposition. This research work was an extension to earlier research published in 2008 by the present authors. The airway geometry applied in this current research was created by closely following the values published by another researcher (Horsfield), where the transient flows for three different breathing cycles were used as the input boundary conditions. The findings of the modelling presented herein indicated that the release position did not vary significantly at different time steps or with changes in particle size, but varied significantly with breathing patterns. Moreover, the rate of particle deposition at the wall was found to increase with the rising of the branching angles.