Abstract

Air pollution is the leading cause of different respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD) that commonly affect respiratory health. Computational fluid dynamics (CFD) has been used to predict the airflow pattern and particle transport within human lungs under disease conditions like obstructed airways. Nevertheless, the combination of the obstructed airways and the aging impact on these diseases under the various flow rates and particle diameters, has not been considered in previous studies. This chapter provides a clear understanding of airflow characteristics and particle transport through obstructions and smaller airways due to aging based on an asymmetric lung model generating from the trachea to the fourth generation. Eight different lung models were used for the numerical simulation. The ANSYS Fluent 19.2 was employed to solve the problems under the finite volume discretization technique. Appropriate grid refinement has been performed for all cases. The results indicate that airflow pattern always changes at the stenosis area. The velocity significantly increases at stenosis area for the first two generations and the smallest diameter size. The maximum pressure drop was located at stenosis area for the first generation of right lung and the fourth generation for the smallest diameter case, whereas the highest pressure was found in the trachea for both conditions. Stenosis areas at first two generations significantly affect higher turbulence intensity while smaller diameters generate lower turbulent fluctuation. The deposition efficiency and deposition fraction were based on the airway volume, particle size, and flow rate. The results of this study enhance the knowledge of airflow characteristics and particle deposition within asymmetric human lungs with stenosis area and smaller diameters.