Lately, an increase in the level of air pollution has become the cause of concern in the medical fraternity. The people who get exposed to air pollutants are prone to develop respiratory problems based upon the duration of their exposure. Hence, to assess the risk probability caused by the pollutants to the pulmonary airways, it is necessary to monitor the number of particles inhaled on a quotidian basis. This would further assist in giving accurate dosage to the ill. Thus, a lung airway of an adult is studied by computationally simulating the three-dimensional non-planar lower three generations (G5-G7) of human lung-airways, based upon the Weibel’s model. The computations are carried out at a Reynolds number (Re) of 1000. Here, the three conditions are taken into consideration, which differ&nbsp;in terms of total particle number concentration and particle size. The sites that are being focused upon are the countryside, C1 (negligibly polluted), and urban sites (i.e. U1) with 22,000 particles introduced uniformly into the airways at the inlet. The particulate injected here is assumed to be non-interactive and spherical. The Discrete Phase Modelling (DPM) application in ANSYS 15.0 is exploited here, which has used the Lagrangian method to track the micro-particles in human airways. Further, the results obtained by present simulations for the axial velocity at the end sections of generation 6 are validated with that of experimental results at Re = 500.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; The evolution of secondary vortices inside the human airways and the deposition of inhaled pollutants across the bifurcation ridge have been analyzed. Enriched secondary flows are observed due to the bifurcations of the airways. Furthermore, the obstructive bronchioles enhance the non-uniformity of secondary flows with multiple vortex cores. The obstruction initially creates ring vortices that end up to spiral vortices after bifurcation. The introduction of inhaled particles brings a more complex flow with the appearance of numbers of swirling streaks that eventually evolve into small-scale eddies like a turbulent flow. Further, particle transport and deposition are influenced by their size, concentration, geometrical structures, and airflow characteristics. The particle deposition increases with particle size and the trapped particles are preferentially accumulated in the upper airways and near the carinal ridge. The particles of size below 5 µm face more retention across human generations, which can prove to be more harmful when deposited to deeper sections of the lungs.Keywords: Pulmonary Airways, Pollutant’s inhalation, Discrete Phase Modelling, Secondary Flows.

A Computational Study Illustrating Secondary Flow and Aerosol Transport in Human Airways

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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