Numerical simulation of aerosol deposition in human upper respiratory tract / 医用生物力学

Objective To study the rule of aerosol deposition in human upper respiratory tract and analyze the impact of respiratory pattern on aerosol deposition. Methods A computer model of human upper respiratory tract was established first. CFD (computational fluid dynamics) method was then used to numerically simulate the aerosol deposition within the human upper respiratory tract and the rule of aerosol deposition was analyzed. Results The efficiency of aerosol deposition in human upper respiratory tract was improved with the increase of inertial parameter. The breathing intensity and aerosol property had little impact on the pattern of aerosol deposition, which was at most in larynx due to the inertial impact and turbulent dispersion. Under the mode of cyclic inhalation, the aerosol deposition efficiency was higher at unsteady respiratory than that at steady respiratory, at cyclic inhalation than at cyclic exhalation. Conclusions Inertial impact is the main key deposition mechanism for micro aerosol, while turbulent dispersion, secondary flow and recirculation flow have an equally important impact on aerosol deposition in human respiratory tract.

Simulation study on characteristics of the vortex structure in human upper respiratory tract / 医用生物力学

Objective The research on vortex structure and vortex evolution in human upper respiratory tract can help to deepen the understanding of the characteristics of the airflow in human upper respiratory tract, which could give some very important assist in analyzing the diffusion, transition and deposition patterns of aerosol in human upper respiratory tract. Methods Large eddy simulation was used to simulate the vortex structure and vortex movement in human upper respiratory tract under the condition of low intensive respiratory patterns, and the vortex structure and vortex evolution in mouth throat model and in trachea triple bifurcation were discussed. Results Jet formations from airflow in pharynx and laryngeal led to two vorticity growth regions; flat vortex appeared in the throat; a curved vortex like the trachea wall appeared in the anterior wall of trachea, and nearly symmetric reverse vortex pairs appeared in the trachea; the vorticity in the G0 trachea end extended from the trachea wall to the center of the trachea, and moved to the G1 bronchial; the vorticity in bronchial of every class presented an asymmetric distribution. Conclusions The vortex structure and vortex evolution are the remarkable characteristics of the airflow in human upper respiratory tract, and the geometric airway characteristics is the main factor that results in the transformation of variable sizes of vortex structures.