Numerical Study On Gas-particle Two-phase Flow In The Upper Respiratory Tract Of Human Body

The human body exchanges gas with the external environment through the respiratory system,and the particles are inhaled into the human body with the inhalation action and deposit in the upper respiratory tract or continue to move to the lower respiratory tract.The research on the movement and deposition of particle in the upper respiratory tract is actually an important application of multiphase flow research in the field of pharmaceutical.It can not only understand the causes of upper respiratory tract infection,the process of virus transmission,and the impact of haze on human health,but also provides the corresponding theoretical and simulation basis for the treatment of upper respiratory tract diseases and inhalation administration,and it is also conducive to the development of multiphase flow mechanism research.This article first reconstructs the three-dimensional image data based on the three-dimensional image of the upper airway taken by CT to establish a true and complete upper airway model,which accurately reflects the geometric structure of the upper airway.The mathematical model of gas-solid two-phase flow based on Euler-Lagrange method was used to study the gas-solid two-phase flow of particles in the upper respiratory tract.Based on the above method,the characteristics of the flow field in the upper respiratory tract with stable inspiratory state under different inspiratory flow were explored,and the flow field under circulating breathing state was compared and analyzed.Due to the complexity of the geometric structure in the upper respiratory tract,as the breathing action progresses,the airflow will produce vortex and return structures in some areas where the cross-section suddenly shrinks,and the maximum value of the velocity appeared due to the airflow jet.With the increase of the inlet air flow,the airflow disturbance in the respiratory tract increases,and the vortex and return structures are more obvious.Based on the calculation of the flow field,the effect of the inspiratory flow,particle size,particle density,Brownian force,Coulomb force on particle movement and deposition.The research results show that with the inhalation of the airflow,the particles enter the upper respiratory tract and deposit.Most of the particles are deposited in the nasal cavity.There is a correlation between the deposition number of particles and the change of the flow field.With the increase of the flow field velocity,the deposition number of particles increases,and the deposition number of particles in the areas with obvious vortex structures is small.The particles with different particle sizes produce different deposition effects under different inspiratory flows.The particles with a particle size of 5?m are generally at the inflection point of change in deposition rate and escape rate.For particles with a particle size of less than 5?m,the deposition rate decreases and the escape rate increases as the particle size increases When the particle density changes,the aggregation degree of the particle deposition increases.Brownian force and Coulomb force have a greater influence on the movement and deposition of small-sized particles.Finally,the particle size distribution of the transport particles was changed,and the multi-component particles were mixed and transported.It was found that the larger particle size,the more densely deposited the nasal cavity entrance and throat area.The larger particles are deposited on the posterior wall surface of the throat area,while the smaller particles are deposited on the front wall surface of the throat area and easier to flow to the lower respiratory tract.