RESUMEN
Objective To develop a measurement device and provide a platform for researching the characteristics of human upper respiratory tract flow field based on PIV (particle image velocimetry) technology with respect to the characteristics that human upper respiratory tract flow may form the vortex structure, flow shunt and secondary flow. Methods A transparent physical model of human upper respiratory tract was prepared based on the completely scanned medical images. By means of selecting appropriate air pressure system, combined with two-dimensional PIV system, a complete experimental apparatus was established. Based on the apparatus, preliminary experiment on air velocity in human upper respiratory tract flow field was conducted, and the experiment result was compared with the numerical simulation result. Results Under the steady breathing pattern at respiratory flow of 30 L/min, respiratory air flow measured by the experimental apparatus led to the formation of vortex structure in the front part of oral cavity. Air velocity was relatively higher both in the lower part of oral cavity near the upper tongue and in the middle part of oral cavity, while the velocity was relatively lower in the other parts of oral cavity. The results were in accordance with numerical simulation. Conclusions The experimental apparatus for human upper respiratory tract flow measurement based on PIV technology is practical and reliable, which can be applied in the measurement of airflow organization patterns and vorticity distributions in human upper respiratory tract, and realize the verification of numerical simulation results.
RESUMEN
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.