(338c) Spectral Element Method for Particle Deposition Patterns in the Human Upper Airway

Particle transport and deposition in the human upper airway have received considerable interest due to the impact these processes have on hazardous as well as beneficial inhaled aerosols. Inhaled aerosols can range from nanoparticles encountered in therapeutic aerosols to 10 micron dust particles. The particle dynamics exhibit a wide spectrum of behaviors from advection dominated to diffusion dominated. Of particular interest to us are the submicron sized particles in secondhand cigarette smoke, which are associated with lung cancer. These particles require close attention to both advection and diffusion.

Beyond capturing the widely varying particle dynamics in the system, accurate deposition analysis also requires a well resolved flow field. The upper airway represents laminar and turbulent flow regimes, a complex geometry, as well as transient inflow conditions. The present study uses the high-order spectral element method to fully resolve the flow field using direct numerical simulation. Spectral elements are adaptable to complex geometries and offer a more accurate solution with fewer grid points. The computer work load and required memory is greatly reduced to allow for high resolution with reasonable computer time compared to conventional methods.

A highly resolved flow field inherently provides a better environment for tracking the particles, and the higher-order elements provide a more accurate solution to the passive scalar advection-diffusion equation. An Eulerian-Eulerian approach can therefore be utilized for wider range of particle sizes as it can capture the advection dynamics of larger Stokes number particles. The results of this study also provide a better understanding of the behavior of nano and submicron sized particle deposition in healthy and diseased lungs as well as a powerful tool to help design therapeutic aerosols.