Numerical simulation of ellipsoidal particles deposition in the human nasal cavity under cyclic inspiratory flow

Abstract

In this study, a computational fluid dynamics model of a 53-year-old nonsmoking Caucasian male was used to simulate the deposition of ellipsoidal particles under cyclic inhalation in the nasal cavity. A sinusoidal pattern (frequency: 0.25 Hz, maximum volume flow rate: 20 L/min) was set to simulate the realistic breathing pattern under a rest condition. In order to find the trajectory of inhaled particles, a series of unsteady particle tracking simulations using a Lagrangian approach were performed and ellipsoidal particles between 1 and 20 µm in size and 1-50 in aspect ratio were injected in the fluid domain. Results showed that for small particles (d = 1 µm), the deposition pattern follows the airflow pattern, and it increases/decreases by an increase/decrease in the inlet volume flow rate. Besides, the deposition is highly sensitive to the shape of the particles, and it rises by an increase in the aspect ratio. Interestingly, for particles in the range of 5-20 µm, the deposition is mainly dependent on the diameter. Also, the deposition pattern of particles with a diameter of 20 µm is entirely different from the deposition pattern of smaller particles, and it does not follow the inlet airflow pattern. Moreover, it was seen that the deposition fraction under cyclic breathing pattern in the acceleration and deceleration phases of the inhalation is not equal. Finally, it was shown that the inertial force has more contribution to the deposition of ellipsoidal particles, and as a result, tracking these particles under the equivalent mean airflow rate (Q = 12.7 L/min) causes significant errors in the total deposition fraction.

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