Numerical Simulation Of The Coagulation Process Under The Condition Of Short-term Respiration Created By The Atmospheric Particulates In Human Lungs

With the increasing impact of human's activities on natural environment,environmental pollution is becoming more and more serious,among which air pollution is the most severe one.Epidemiologic studies have shown that rise of inspirable particle concentration in the atmosphere could lead to an increase of morbidity and mortality in many diseases.Particulates are supposed to enter the respiratory system through nasal cavity or oral cavity during the process of respiration,of which those with smaller particle may enter the lungs and deposit in different locations,and then causing various types of diseases.Therefore,particle size and deposition location are two key factors for atmospheric particulates in effecting human's health.In view of the fact that the above phenomenon researches are mainly from the perspective of the transmission created by particulates in the lungs,this paper uses the theory of coagulation dynamics as a base,and discusses the evolution process of atmospheric particulates when entering human lungs,under the condition of short-term respiration.It starts from the following three questions:(1)The feasibility of using the coagulation dynamics model in the study of the evolution issues in human lungs brought by the particulates;(2)The evolution rules of the particulates when entering human lungs;(3)Factors affecting the deposition of particulates in human lungs.During the research,this paper establishes particle collision frequency function,on account of Fuchs' transition zone coagulation theory,and other two coagulation sedimentation models(Lagrangian 's and Eulerian's).It also takes a combination of Hounslow coagulation dynamics model and MATLAB software aided calculation,simulating the evolution process of particulates in Weibel lung space.The results show that Hounslow coagulation dynamics model is suitable for the study of the evolution issues in human lungs brought by the particulates.The evolution rules of particulates after they enter human lungs are as follows:(1)Under the condition of short-term respiration,particulates are bound to have the phenomenon called'Coagulation particle size grown-up';(2)The particulates grow up into a steady state when at each level of the bronchi,and the particle size is higher than the upper level when it is at a stable state;(3)Time spent from the non-steady state to the steady state decreases with the increasing bronchial levels.In addition,the deposition of particulates in human lungs is affected by the initial particle size of the particulates,the amount of human respiration,and the depositing position,which is embodied in the fact that boosts in the initial particle size and breathing volume can promote the deposition of particulates in human lungs,and the deeper the depositing position,the smaller the fraction of deposition.