NUMERICAL SIMULATION OF THE DISPERSION AND DEPOSITION OF A SPRAY CARRIED BY A PULSATING AIRFLOW IN A PATIENT-SPECIFIC HUMAN NASAL CAVITY

The present numerical study concerns the dispersion and deposition of particles in a patient-specific human nose for steady and pulsating airflow conditions. The realistic three-dimensional geometry of the nasal cavity is reconstructed from a computer tomography (CT) scan. An unsteady Eulerian-Lagrangian formulation is used to describe the airflow and the spray dispersion and deposition in the realistic human nasal airway using two-way coupling between the gas and the liquid. A large eddy simulation (LES) with the dynamic Smagorinsky sub-grid scale (SGS) model is performed to study the spray in both a steady and a pulsating airflow with inflow rates of 4.78 L/min and 7.5 L/min for the steady case and a maximum inflow rate of 7.5 L/min and a frequency of 45 Hz in case of the pulsating spray as used in commercial inhalation devices. 10,000 mono-disperse particles with the diameters of 2.4 and 10 mu m are uniformly and randomly injected at the nostrils. The airflow velocity reaches maximum values in the nasal valve, in parts of the septum, and in the nasopharynx. A complex airflow is observed in the vestibule and in the nasopharynx region, which may directly affect the dispersion and deposition pattern of the spray. The results reveal that the spray tends to deposit in the nasal valve, the septum, and in the nasopharynx due to the change in the direction of the airflow in these regions. Moreover, it is found that for the pulsating inflow, the aerosols are more dispersed and penetrate deeper into both the posterior regions and the meatuses where the connections to the sinuses reside.