ABSTRACT
Objective To investigate the airflow distribution mode in human upper respiratory tract model for understanding the characteristics of the airflow in human upper respiratory tract, and provide scientific basis for analyzing the diffusion, transition and deposition patterns of aerosol in human upper respiratory tract. Methods PIV（particle image velocimetry）technology was adopted to study flow fields of the real human upper respiratory tract model. The airflow state in oral cavity，pharynx and trachea was analyzed. Results The flow velocity was relatively high at the upper tongue coating and in the middle of the oral cavity; when the airflow reached the pharynx, the velocity was increased rapidly due to the reduction of sectional area; the maximum velocity (10.24 m/s) appeared in the glottis, and the velocity in the anterior wall was higher than that in the posterior wall of the trachea; as the airflow injected at the glottis, the velocity gradient was increased, and the vorticity was concentrated at the anterior and posterior wall of the glottis, resulting in a significantly higher vorticity value at anterior wall of the trachea than that at the posterior wall. Conclusions PIV technology is an effective way to investigate the airflow distribution mode in human upper respiratory tract, and it is of great importance for exploring the harm of toxic aerosol to human body and the therapeutic effect of inhalation drug aerosol, as well as for researching the pathogenesis of respiratory system.
ABSTRACT
Objective To study the vortex structure and vortex evolution induced by jets in mouth-pharynx area, so as to deepen the understanding of jet motion characteristics and disease prevention in mouth-pharynx area. Methods CT scanning and 3D reconstruction were used to construct 3D model of realistic human mouth-throat model, and the method of large eddy numerical simulation was used to accurately simulate the process of vortex evolution in the model. ResultsIn the phase of inhalation, several vortex tubes were formed in mouth, and a turbulence jet appeared in the glottal region. In the phase of exhalation, the intense jet in the glottal region caused complex vortex structures in throat. Conclusions During inhalation, transition occurrs in the pharynx, and the “horseshoe vortexes” which are similar to the shape of horseshoe appeared on the anterior wall of the trachea. During exhalation, “arch vortex” are formed on the posterior wall of throat with the barrier of epiglottis.
ABSTRACT
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.
ABSTRACT
Objective To examine the aerosol particle deposition in human upper respiratory tract model and explore the pathogenesis of toxic aerosol in human upper respiratory tract. MethodsA human upper respiratory tract model was constructed using ABS (Acrylonitrile Butadiene Styrene) plastic, and an experimental system was established to measure the deposition efficiency of aerosol particles with different diameters (0.3 or 6.5 μm) at different breathing intensity (30 or 60 L/min) in this model. Results The deposition patterns of aerosol particles with different diameters and at different breathing intensity in human upper respiratory tract model were similar. The deposition efficiency was generally higher in pharynx，larynx and trachea while being the highest in the area of larynx. Conclusions The breathing intensity has a major impact on aerosol deposition efficiency in the model. Larger aerosol particles are more easily to deposit in the model. Inertial impaction and turbulence intensity are the main mechanisms of aerosol particle deposition.
ABSTRACT
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.