【作者】 孙栋；

【导师】 徐新喜；

【作者基本信息】 中国人民解放军军事医学科学院 ， 卫生防护防疫技术与装备， 2012， 博士

【摘要】 人体上呼吸道是呼吸系统的重要组成部分，是人体与外界环境进行气体交换的主要通道。随着国际生物恐怖威胁的增加、大气环境的不断恶化以及卫生防护防疫技术的发展，人体上呼吸道内气流运动与气溶胶扩散研究的重要性已越来越为人们所关注。当遭遇生物恐怖袭击时，大量的病毒气溶胶通过上呼吸道进入人体内，对人体造成极大危害；具有生物污染物防护功能的卫生舱室虽然能够对绝大部分病毒气溶胶进行有效过滤，但仍有少量有毒气溶胶进入舱室，并通过上呼吸道对人体造成危害；空气污染所导致的呼吸系统疾病的发病率逐年增加，其复杂性和严重性也日益突出，严重影响了人们的生活质量。本文通过构建人体上呼吸道三维规范模型，采用数值模拟和PIV流场可视化实验研究相结合的方法，对流固耦合作用下稳态呼吸和瞬态循环呼吸过程中上呼吸道规范模型内的气流组织、涡结构演化以及气溶胶颗粒扩散沉积进行了数值仿真研究，并进行了实验验证。主要工作及研究结果如下：构建了人体上呼吸道三维规范几何模型。运用三维重建技术和高级图像处理技术，通过上呼吸道CT扫描、个体上呼吸道三维重建、个体模型归一化处理、个体模型切片、切片图像融合处理、模型规范化处理等步骤，构建了人体上呼吸道三维规范模型，并对其进行了定性与定量分析，结果表明：与以往的简化模型相比，规范模型在几何形状真实性、结构特征完备性方面与真实人体上呼吸道更接近，在科学研究方面具有更高的应用价值。分析了人体上呼吸道内的流固耦合作用。通过构建和运用人体上呼吸道流固耦合力学模型，分析了流固耦合作用下人体上呼吸道壁面的形变状况和呼吸道内的气流组织特征，结果表明：流固耦合作用下，呼吸流量越大，呼吸道形变越大，对气流的缓冲能力越强；吸气时，咽喉部位及气管处向后方移动，咽喉部位受到气流运动的作用，出现扩张现象；呼气阶段，咽喉部位及气管处向前运动，咽喉部位受到气流运动的作用，出现收缩现象。循环吸气过程中，气流分别在咽部和喉部形成两个速度增长点，在咽部气流发生分离现象；在声门位置受到几何结构的限制，产生湍流喷射的现象；声门处的喷射致使气流在气管前壁处形成高速气流，气管后方形成流动分离现象；随着与声门距离的增加，气管前、后壁气流速度差逐渐减少。循环呼气过程中，口腔顶部贴近软腭和硬腭部位的气流速度要高于口腔底部，且在口腔顶部发生流动分离现象，形成分离区；在支气管的分叉处，气流发生交汇现象，交汇造成分叉中心处形成低速区，而交汇气流使上一级支气管中产生暂时的两个气流高速点，随后逐步合并。模拟了流固耦合作用下人体上呼吸道内的涡结构演化过程。运用大涡模拟和流固耦合数值仿真方法，对人体上呼吸道内涡结构演化过程进行了分析，结果表明：吸气过程中，气流进入口腔，硬腭部位气体与入口气流发生“互搓”，加上口腔中舌苔的阻碍，致使气流在口腔中部以及舌苔上部形成了多个涡管结构，随后受到咽部复杂结构的强烈干扰以及气道的转向，入口气流发生转捩；气流在声门部位形成强烈的射流，射流沿着气管的前壁向前发展，受到气管前壁形状的影响，在气管前壁处出现了类似于马蹄形状的“马蹄涡”。呼气过程中，气流在气管支气管的分叉处发生交汇现象，在气管的底部产生了较为复杂的涡结构，随着气流在气管内的融合，气管内的涡量逐步减弱，只剩一个能量较大的涡管沿着气道不断伸长；气流在声门处的强烈喷射以及会厌部位的阻碍使咽喉部位产生了较为复杂的涡结构，在咽喉后壁处射流受到阻碍，形成了“拱状涡”；进入口腔时，气流受到软腭阻碍、气道转向以及截面缩小的影响，一方面导致咽腔内的大的涡结构发生破裂，另一方面致使气流在咽部再次发生喷射，射流朝向口腔上部，口腔内并没有较大的涡结构产生。研究了流固耦合作用下人体上呼吸道内的气溶胶扩散沉积行为。借助Lagrangian随机轨道模型，对规范模型内的气溶胶颗粒扩散沉积进行了仿真分析，结果表明：吸气过程中，0.3m的气溶胶颗粒比6.5m的气溶胶颗粒更容易通过上呼吸道，进入更深层次的支气管中；0.3m的气溶胶颗粒更容易受到涡结构的影响，喉部后侧以及气管后部具有螺旋状轨迹的气溶胶颗粒数量更多；大多数的气溶胶颗粒将在上呼吸道模型中的涡量集中区通过。呼气过程中，部分进入上呼吸道模型的颗粒在呼出气流的夹带下，在气道中折返、回旋、沉积，而有些则从口腔中呼出，在折返的过程中，由于颗粒对于呼出气流的跟随性较好，折返的轨迹主要集中呼吸气阶段涡量集中的区域。呼吸流量30L/min和60L/min时粒径分别为0.3m和6.5m的气溶胶颗粒在喉部及气管内沉积较多，但在口腔内的沉积较少；6.5m的气溶胶颗粒在上气道不同部位的沉积率要明显高于0.3m气溶胶；在考虑流固耦合作用时，两种粒径的气溶胶颗粒在咽喉部位的沉积率均有所下降；粒径为6.5m气溶胶的主要沉积机理是惯性碰撞，而粒径为0.3m的气溶胶的沉积却主要受到湍流扩散及涡流夹带的影响。开展了人体上呼吸道内气流组织、涡结构演化及气溶胶沉积的可视化实验。利用激光固化快速成型（Stereolithography，SL）技术制备了人体上呼吸道三维规范实物模型，并运用流场可视化测试（Particle Image Velocity，PIV）技术对其内部气流组织、涡结构演化及气溶胶沉积进行了实验测量，将实验测量结果与仿真结果进行对照，从而验证了数值仿真方法的正确性，结果表明：实验测量结果与仿真结果整体气流组织形式较为一致，实验中最大速度为10.24m/s，仿真中最大速度为9.55m/s，且测量数值与仿真数值误差最大不超过8%，气溶胶颗粒在人体上呼吸道内各部位的沉积趋势基本一致，吻合较好，从而说明数值仿真方法的准确性。更多还原

【Abstract】 Human upper respiratory tract is an important part of respiratory system andthe main exchange channel for gas between the body and the outside environment.With the increase in threat of international bioterrorism, the development of sanitaryprotection and epidemic prevention technology and the deterioration of atmosphericenvironment, the importance of the research on airflowment and particle diffusionin human upper respiratory tract have gradually aroused more attention. Whenbioterrorism attacks happen, a large number of virus aerosols entered and do harmto human body via upper respiratory tract. Although most of virus aerosols can befiltered effectively by sanitary cabin with the function of biological protection, thelittle can also entered the cabin and accumulated in human body, which also candamage human health. The incidence of respiratory diseases caused by atmospherepollution increased year by year, and the complexity and severity of the diseases isincreasingly outstanding, which has seriously influenced the quality of life.The standardized model of human upper respiratory tract was constructed, andthe methods of integrating numerical simulation with PIV experimental researchwere used to study the airflowment, vortex evolution and aerosol deposition in thestandardized model under the effect of fluid-solid interaction both in steady andcyclic respiratory pattern. The main conclusions of the present work aresummarized as followed:The3D standardized model of human upper respiratory tract wasconstructed. The technology of3D reconstruction and sophisticated imageprocessing was used to construct3D standardized model of human upperrespiratory tract by the processes of CT scanning for upper respiratory tracts,3Dreconstruction of individual upper respiratory tract, normalization of individualmodels, slicing individual models, fusion of slicing image and standardization ofthe model, and then the difference between standardized model and the previousmodel was analyzed qualitatively and quantitatively. The results show that:compared to the simplified model, the standardized model is more similar to the realhuman upper respiratory tract in the completeness of structural characteristics andthe reality of geometry, and it possesses more application value in scientificresearch.The fluid-solid interaction was analyzed in human upper respiratory tract. The fluid solid interaction mechanics model is built and used to simulate airflowmovement in human upper respiratory tract model, and the shape change of themodel wall and the airflow in the model were analyzed. The results show that:Under the effect of fluid-solid interaction, the larger the respiratory flow is, thegreater the shape of respiratory tract changes, and the stronger the buffer effectworks on the airflow. In the phase of inhalation, the throat and trachea movebackward, the anterior wall was stretched, and the posterior wall was compressed,meanwhile airflow movement causes the expansion of throat. In the phase ofexhalation, the throat and trachea moves forward, the anterior wall was compressed,and the posterior wall was stretched, meanwhile airflow movement causes theshrinkage of throat.In the phase of cyclic inhalation, high velocity zone is created in pharynx andlarynx, and the phenomenon of airflow separation appeared in the pharynx. Aturbulence jet appears in the glottal region because of the restriction of geometricstructure, and the airflow separates in the downstream of the glottis with theseparation zone appearing near the posterior wall of the upper part of the trachea,and with high velocity zone appearing near the anterior wall. With the increase inthe distance with glottis, the velocity difference between the anterior and posteriorwall of the trachea gradually decreases. In the phase of cyclic exhalation, thevelocity of airflow near the hard palate and soft palate is higher than that on thebottom of mouth, and the phenomenon of airflow separation appears on the top. Theairflow streams converge at the bifurcation of trachea and bronchi, which causes thevelocity in the center of the bifurcation is lower. Meanwhile the confluence alsocauses two temporary airflow streams with higher velocity appear in the superiorbronchus, and then converges gradually.The vortex evolution in human upper respiratory tract under the effect offluid-solid interaction was simulated. Large eddy simulation and fluid-solidinteraction mechanics was used to simulate the process of vortex evolution and theresults show that:In the phase of inhalation, several vortex tubes were formed in the central ofmouth because the air near the hard palate rubs against the inlet airflow streams andwith the barrier of tongue coating some vortex tubes also appear on the surface oftongue coating. Then, transition occurred in the pharynx with disturbance of softpalate and the turning of airway. A turbulence jet ejected towards to the anteriorwall of the trachea appeared in the glottal regional. Affected by the barrier of thetrachea wall, the “horseshoe vortexes” which are similar to horseshoe appeared onthe anterior wall of the trachea.In the phase of exhalation, the airflow streams converged at the bifurcation of trachea and bronchi, and the confluence caused the complex vortex structure on thebottom of the trachea. With the airflow streams converging, the vorticity in thetrachea decreased, and only a stronger vortex tube was extended along with thetrachea. The intense jet in the glottal regional and the barrier of epiglottis causedcomplex vortex structures in throat, and “arch vortex” are formed on the posteriorwall of throat. When the airflow entered the mouth, the vortex structures broke upand a jet was ejected towards to the top of mouth because of the barrier of softpalate, turning of the airway and the shrinkage of cross-section in pharynx, in themeanwhile, there were no big vortex structure in the mouth.The diffusion and deposition of aerosol particles in human upper respiratorytract under the effect of fluid-solid interaction was studied. The lagrangianstochastic trajectory model and fluid-solid interaction mechanics were used tosimulate the deposition and diffusion of the aerosol particles, and the results showthat:In the phase of inhalation, the aerosol particles with size of0.3mwere morelikely to pass through upper respiratory tract and get to the lower bronchus than theparticles with size of6.5m. Easily affected by the vortex structures, more aerosolparticles with size of0.3mwith the helicoidally trajectories appeared on theposterior wall of larynx and trachea, and most of particles passed through theregions with higher airflow vorticity. In the phase of exhalation, the aerosolparticles entrained by the exhalation flow returned, convoluted and deposited in thetract. And some of the aerosol particles were taken out of mouth during this process.The trajectories of the reentrant particles were congregated in regions with higherairflow vorticity due to the good following performance of the particles.Both under the conditions that the respiratory flow are30L/min and60L/min,the deposition fraction of the aerosol particles with sizes of0.3mand6.5minthroat and trachea was high, and that in the mouth was low. And the depositionfraction of the aerosol particles with size of6.5min different zones of the upperrespiratory tract is obviously higher than that with size of0.3m. With the effect offluid-solid interaction, the deposition fractions of the sizes of0.3mand6.5min the throat will decrease. The main mechanism of deposition for the particles withsize of6.5mis inertial impaction, and the deposition for the particles with size of0.3mis more likely to be effected by turbulent dispersion and entrainment ofeddy current.The visualization experiment researches on airflow movement, vortexevolution and aerosol deposition were performed. The Stereolithography (SL)technology was used to construct the replica of human upper respiratory tract for experiment, and the Particle Image Velocity (PIV) technology was applied tomearsure the airflow movement, vortex evolution and aerosol deposition. The resultfrom the experiment was contrasted with that from simulation, which vertified theaccuracy of the simulation method. The results show that: the result of experimentis consistent with that of simulation in the air distribution mode. The maximumvelocity in the simulation is10.24m/s, and that in the experiment is9.55m/s. Themaximum error of the velocity between the two results is not over8%, and the trendof the aerosol deposition in the parts of human upper respiratory tract wasconsistent, which both verified that the numerical simulation methods are accurateand reasonable.更多还原