Transport and Deposition of Ellipsoidal Fibers in Subject-Specific Lung Airways

Fine to ultrafine materials, such as spherical particles and fibers with their diverse applications ranging from cosmetics, cleaners and composites to nanomedicine are increasingly ubiquitous in the air we breathe. For example, the unique lung deposition patterns of nanoparticles and their ease-of-migration into the blood stream may cause severe health problems, as discussed by Oberdoerster et al. (2005). In contrast, multifunctional nanoparticles as well as micron fibers are also being used as drug carriers for cancer treatment (Zhang et al., 2011). While the transport and deposition of spherical nanoparticles has been analyzed (Kleinstreuer and Zhang, 2010; among others), the fate of ellipsoidal particles in subject-specific lung airways has hardly been addressed. In this study, the Euler-Lagrange fluid-particle modeling approach (i.e., the Discrete Phase Method solver) has been employed in Fluent 13.0 (ANSYS, Canonsburg, PA). User-supplied C-programs have been added to simulate ellipsoidal fibers transport and orientation effects. The computer simulation model has been validated for fiber transport and deposition in a circular tube (Tian et al., 2012). Additionally, transitional airflow patterns were analyzed and local deposition efficiencies compared for spherical particles and fibers in a realistic human respiratory system. The capability of ellipsoidal fibers migrating into deeper lung regions was indicated and fiber deposition “hot spots” were discussed. The numerical results expand the basic understanding of the dynamics of non-spherical particles in realistic shear flows, and can be used to investigate the fate of inhaled toxic or therapeutic materials.