Characteristic of Gas-Solid Two-Phase Flow in the Human Upper Respiratory Tract Model

The CFD (Computational Fluid Dynamic) technology was used to investigate the air movement characteristic and aerosol deposition in the human upper respiratory tract. Steady and cyclic respiratory with the breathing intensity of Q = 30 L/min and aerosol diameter of d = 0.3, 6.5 mum were considered. Experimentally validated computational fluid-aerosol dynamics results showed the following: the phenomenon of airflow separation appears near the outer wall of the pharynx and the trachea. The high velocity zone is created near the inner wall of the trachea. The airflow splits at the divider and a new boundary layer is generated at the inner wall of the downstream from the bifurcation with the high velocity near the inner wall of the trachea. The maximum velocity appears at the exterior of the boundary layer. The secondary swirls and axial velocity distribution result in the high shear stress acting on the inner wall of the trachea and bifurcation, finally lead to the inner wall injury. The inertial impaction is the main mechanism for the micro-aerosol deposition. The turbulence dispersion, secondary airflow movement and the airflow recirculation motion influence the aerosol deposition in the human upper respiratory tract. Most aerosols deposit in the larynx due to the turbulence dispersion and inertial impaction. The aerosol deposition in the cyclic respiratory pattern is higher than in the steady respiratory patter and the aerosol deposition in the cyclic inhalation is higher than in the cyclic exhalation.