Microfiber transport characterization in human nasal cavity – Effect of fiber length

Abstract Understanding the transport and deposition of fibers in the respiratory airway is of great significance for the exposure assessment to non-spherical contaminants. Due to its complexity, few computational studies physically resolved the fibers' coupled translational and rotational motion in investigating fiber transport behaviors in the 3D human nasal airways. Additional studies are needed to fully understand the role of the fiber lengths in nasal deposition and the practical benchmarking of fiber characterization to its spherical equivalency. This study investigated the transport and deposition of fibrous particles in the human nasal cavity, resolving the coupled translational and rotational motion to fill the gap. For the first time, a detailed single fiber trajectory in the 3D nasal chamber, accounting for the coupled translational and rotational movement, was visually presented. The subtle effects of fiber deposition due to fiber lengths, rotation, and interaction with the local flow stream, were revealed and analyzed. Furthermore, the study identified the relationship between microfiber deposition and fiber lengths in the human nasal cavity. In particular, nasal deposition of the fibrous and spherical particles with the same impaction parameter or aerodynamic diameter was compared and discussed. The study led to the findings that fiber lengths play different roles in affecting the transport and deposition of microfibers in the human nasal cavity. The relative deposition level between elongated fibers and the spherical particles varies depending on the impaction parameter or the aerodynamic diameter. Current findings are well supported by the literature data.