Inhalation, evaporation and deposition of water droplets at nostrils under cyclic flow

Despite many investigations about transport and deposition of particles in the human nasal cavity, there are still debates about the boundary conditions and assumptions. Besides, some particles undergo phase change that influences deposition and penetration of particles to deeper regions in the human respiratory system. This paper compared two types of particle injection with a spherical breathing zone, and direct particle injection from nostrils for droplets and non-evaporating particles. A cyclic breathing condition was applied, and micro-particle inhalation, transport process, evaporation, and deposition were numerically simulated using the Lagrangian trajectory approach. The size change of droplets was simulated by implementing a convection-diffusion model and user-defined functions (UDF) for ultrafine droplets. The results showed a significant difference in particle distribution and deposition spots at nostrils, which is Due to the differences between the streamlines in both case studies. In the realistic case with breathing zone, particles experience smoother path lines, but for nasal cavity without breathing zone particles faces sharper curvatures, which raises the chance of impaction and deposition at the anterior part of the nasal cavity. Also, the temperature contour at the nasal inlet has a direct effect on the distribution of water droplets, which is more evident in the cyclic flow.

Keywords:

Particle deposition , Nasal cavity , cyclic flow , Evaporation , Droplet