Effect of Microfiber Length on Microfiber Motion in Human Nasal Airways

Respiratory inhalation of elongated mineral particles has been a significant concern for humans due to the adverse health consequences. In recent years, the increased usage of carbon nanofiber and carbon nanotubes in high-performance engineered materials has raised renewed concerns. However, studies on this subject are still limited, and many aspects of the respiratory deposition of elongated microfibers are not fully understood. In this study, simulations of the transport and deposition of elongated microfibers in a realistic human nasal cavity model were performed. A constant breathing rate of 15 L/min under laminar flow conditions was assumed, and the airflow field was evaluated using the ANSYS FLUENT™ 19.2. Motions of the elongated ellipsoid were simulated using the coupled translational and rotational governing equations, accounting for the hydrodynamic drag and torque, shear-induced lift, and gravitational sedimentation utilizing an in-house microfiber code incorporated in the ANSYS FLUENT™ UDF (user Defined Function). Sample single microfiber trajectories were presented and analyzed to provide insight into their motions. In addition, the microfiber deposition due to microfiber lengths, rotation, and interaction with the local flow stream, were investigated.