Numerical study on the impact of mucus layer and inlet air-temperatures on the particle deposition in a highly idealized mouth-throat model using LES

Presence of mucus layer and inlet air temperature variations can significantly affect the extent of particle transport and deposition in the mouth-throat airway for aerosol drug delivery applications. In addition, higher inlet air temperature can lead to thermal injuries as well. The main goal of the present paper is to investigate these effects in a highly idealized mouth-throat geometry in detail. Large eddy simulation was performed to accurately predict the air flow-fields and a Lagrangian particle tracking model has been employed to capture the particle deposition efficiencies and patterns. The effects of three different inlet air temperatures (15 °C, 26.7 °C and 45 °C) and three different particle sizes (3 μm, 5 μm and 6 μm) have been studied for inlet flow rates of 15 L/min and 30 L/min with and without mucus layer in the present investigation. Detailed velocity and temperature fields, as well as, particle deposition efficiencies and patterns were analyzed and it has been found out that (a) the particle deposition efficiencies varied significantly with changes in inlet air temperature and flow rates, particle diameters and in the presence of mucus layer, (b) the presence of recirculation zones and secondary vortices determined the rate of particle deposition at different inhalation flow rates and inlet air temperatures, and (c) the changes in temperature distribution near the mouth-throat wall in the presence of mucus layer have a dominant effect on particle deposition as compared to inertial deposition. The findings of the present work will provide useful information in understanding the heat transfer effects on particle transport and deposition for the design of pulmonary drug delivery devices under the influence of various environmental and human factors.