The Simulation Of Pulmonary Mass Transport Based On The Symmetry Characteristics Of Bifurcated Pipeline

It was very important to study the influence of respiration on the deposition of particles and the characteristics of gas transmission.For example,when fire occurred,people were in a high concentration of flue gas.Toxic and harmful gases entered human respiratory tract easily.When the harmful substances were inhaled to the pulmonary acinus which undertakes respiratory function,it would seriously endanger human health because it could break through the air blood barrier into the vessels.The depth and concentration of toxic and harmful gas entering the lung directly affected the survival time of people in the fire.On the other hand,inhalation therapy was a new approach to treat respiratory diseases by the using drug particles deposited in the pulmonary acinus.Because of its high bioavailability and high efficiency,it has been considered as a promising therapy method in recent years.This paper is based on the multidimensional bifurcation of healthy adult lung models,with the rational simplification and improvement of the simulation conditions,to investigate the effects of particle deposition and gas transportation on lungs in different respiratory statement such as Sedentary Tidal Volume(TV),Inspiratory Capacity Breathing(IC),High Frequency Oscillation Breathing(HFO)and breath holding.In this paper,numerical simulation is conducted in the commercial software,COMSOL Multiphysics 4.3a.Firstly,we used the 2D,eight generations model of pulmonary alveoli to study the effect of gravitational direction on the particle deposition characteristics of pulmonary alveolus,.The results showed that the directions of gravity had negligible effect on the whole deposition of pulmonary acinus,but it could affect the generation deposition.Relative to the vertical direction of gravity,the horizontal gravitational direction can increase the generation deposition fraction in the specific area.Secondly,based on the Weibel-A lung model,we established a 2D,4-23 generations adults model by symmetrical simplification,and the effects of different respiratory modes on the gas transport were studied.The results showed that the gas diffused very rapidly in the lungs and reached the pulmonary acinus in the first inspiratory cycle.Through the comparison of HFO,IC and TV,it was found that the diffusion rate of HFO and TV were the same,and that in the IC spreads faster.Through the comparison of the circular breathing and breath holding,it was found that breath holding can slow down the diffusion of lung gas.Through the comparison of different breath holding model,the transmission velocity of TV breath holding was the slowest,followed by the HFO breath holding and the IC breath holding.Finally,in the whole lung model,the difficulty of calculating the particle deposition in multistage bifurcation network was proposed,and the particle doubling scheme was proposed to solve the problem of particle transport and deposition in multistage bifurcation network.The velocity and trajectory of the primary particles and the secondary particles were analyzed.Then the particle doubling scheme was used to calculate the particle deposition in the bifurcation network and to demonstrate the feasibility and superiority of the particle doubling scheme.In this paper,the particle doubling scheme can not only simplify the numerical simulation of the whole lung particle deposition,but also can be used in the study of river or air conditioning pipelines and other multi-generation bifurcation networks.