雾霾颗粒在人体呼吸道内的运动沉积机理的研究

发布时间：2018-06-06 08:51

本文选题：气固两相流 + 流固耦合　；参考：《苏州大学》2016年硕士论文

【摘要】：当今的世界面临着日益严重的大气污染问题,随着汽车等工业产品的普及以及沙尘肆虐等灾害的频发,雾霾现象出现频繁,呼吸道疾病的患病率大幅上升。通过研究雾霾颗粒在人体呼吸道内运动和沉积的机理,对于相关的生理和病理研究具有重大的研究意义和理论价值。本文采用计算流体动力学方法,建立了颗粒物在人体呼吸道的气固两相流模型,在考虑纤毛驱动粘液运动的流固耦合机制的基础上,建立了颗粒物在粘液纤毛系统中的运动模型,并进行了相关的数值仿真计算。不仅从宏观领域上探讨了雾霾颗粒物的沉积机理,而且在微观领域上对颗粒物在呼吸道壁面沉积后的运动规律进行研究和探讨,通过和现有的实验数据以及文献的对比,证明了本文的数值计算模型以及计算方法的有效性和正确性。本文首先阐述了计算流体动力学的基础理论,对颗粒在呼吸道内空气流中的运动建立气固两相流模型,选用大涡模拟描述呼吸道内气流的运动;分析颗粒物在空气流中的受力情况,采用DPM模型追踪颗粒在呼吸道内的运动轨迹。然后,在人体上呼吸道物理模型基础上建立刚性和弹性的呼吸道模型。研究呼吸强度为30L/min和90L/min时,稳态呼吸模式和循环呼吸模型下的气流运动特性,计算结果表明:由于呼吸道几何结构的限制,气流在声门处会产生湍流喷射现象,在声门上下游气管外壁附近会发生气流分离,产生回流现象;循环吸气过程中,呼吸道内的气流轴向速度增大,在咽部和声门下游气管外壁处产生更为明显的涡流现象;在呼吸道的弹性壁模型计算中,随着呼吸道壁发生位移和变形,在口腔底部及咽喉部位,由于局部壁面出现凸起扩张现象,其膨胀的呼吸道壁对内部运动的气流将起到“缓冲”的作用,降低气流的速度。在此基础上,分别对0.3um、2.5um和6.5um粒径的颗粒沉积规律进行研究,并考虑不同颗粒浓度下对颗粒沉积的影响,从而揭示了颗粒在呼吸道内的运动沉积机理:颗粒粒径的大小和人体呼吸强度是颗粒沉积最主要的两个因素。不同粒径颗粒的沉积机理不尽相同,湍流扩散和涡流夹带对于0.3um粒径的颗粒是其沉积的主要因素;惯性碰撞对于6.5um粒径的颗粒影响最大;对于2.5um粒径的细颗粒的沉积,惯性碰撞和湍流扩散对此粒径的作用十分明显。最后,选取PM2.5在支气管内的沉积区域的微尺度系统-粘液纤毛系统进行研究。研究该区域纤毛摆动规律,建立纤毛运动模型;分析粘液分布情况,建立具有自由液面边界的VOF粘液流场模型。考虑纤毛簇状分布的现象,建立了流固耦合作用下的呼吸道粘液纤毛系统,研究在纤毛正常摆动情况下,上方粘液层及附着颗粒物的运动情况,计算结果证明了颗粒物在粘液纤毛系统中受到“清除”机制的作用。
[Abstract]:Nowadays, the world is facing more and more serious air pollution problems. With the popularization of industrial products such as automobiles and frequent disasters such as dust raging, the phenomenon of haze appears frequently, and the prevalence of respiratory diseases increases significantly. It is of great significance and theoretical value to study the mechanism of movement and deposition of haze particles in human respiratory tract. In this paper, a gas-solid two-phase flow model of particulate matter in human respiratory tract is established by using computational fluid dynamics (CFD). The fluid-solid coupling mechanism of ciliated mucus motion is considered. The motion model of particulate matter in mucociliary system was established and the relevant numerical simulation was carried out. Not only the deposition mechanism of haze particles is discussed from the macroscopic field, but also the motion law of particulate matter after deposition on the respiratory tract wall is studied and discussed in the micro field. The results are compared with the existing experimental data and literature. The validity and correctness of the numerical model and the calculation method are proved. In this paper, the basic theory of computational fluid dynamics (CFD) is introduced, and a gas-solid two-phase flow model is established for the movement of particles in the airflow in the respiratory tract. The large eddy simulation is used to describe the movement of the airflow in the respiratory tract. DPM model was used to track the movement of particles in the respiratory tract. Then, based on the physical model of human upper respiratory tract, a rigid and elastic model of respiratory tract is established. The characteristics of airflow movement in steady breathing mode and circulatory breathing model with respiratory intensity of 30L/min and 90L/min are studied. The results show that due to the limitation of respiratory tract geometry, turbulence jet will occur in glottis. The flow separation will occur near the outer wall of the trachea in the upper and lower reaches of the glottis, and the reflux phenomenon will occur, and the axial velocity of the airflow in the respiratory tract will increase, and the vortex phenomenon will be more obvious in the outer wall of the trachea in the pharynx and the lower part of the glottis. In the calculation of elastic wall model of respiratory tract, with the displacement and deformation of respiratory tract wall, the local wall appeared bulge and dilation phenomenon in the bottom of mouth and throat. The inflated respiratory wall acts as a buffer against the internal movement of the airflow and slows down the velocity of the airflow. On this basis, the particle deposition of 0.3um 2.5 um and 6.5um particle size was studied, and the effects of different particle concentrations on the particle deposition were considered. Therefore, the mechanism of particle movement and deposition in respiratory tract is revealed. The particle size and human respiratory intensity are the two main factors of particle deposition. The deposition mechanism of different particle size is different. Turbulent diffusion and eddy current entrainment are the main factors for the deposition of 0.3um particle, inertial collision has the greatest influence on the particle size of 6.5um, and for the deposition of fine particle size of 2.5um, the main factor is the effect of turbulence diffusion and eddy current entrainment on the deposition of 6.5um particle. The effect of inertial collision and turbulent diffusion on the particle size is very obvious. Finally, the microscale system of PM2.5 in the deposition area of bronchus, mucociliary system, was selected to study. The ciliated motion model is established and the VOF mucus flow field model with free liquid surface boundary is established by analyzing the mucus distribution. Considering the phenomenon of ciliated cluster distribution, a respiratory mucociliary system under fluid-solid coupling was established, and the motion of the upper mucous layer and attached particles was studied under the normal cilium swinging. The results show that particulate matter is "scavenging" mechanism in mucociliary system.
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X513

【相似文献】