The Numerical Simulation Research On Airflow Patterns And Micro-particle Deposition In The Three Dimensional Pulmonary Acinus

Inhalable particles deposition in respiratory is harmful to the health of the human. Recently, with the increasing of environment pollution, the morbidity and mortality of respiratory system diseases are increasing rapidly, especially fine particles can deposit in the alveolar walls, even penetrate into the blood circulation system, affecting the heart and brain. On the other hand, inhaling aerosol therapy is recognized as a promising method for treating the respiratory diseases worldwide. How to transport the aerosol drug to the disease sites and improve the treatment effect is still worth studying Therefore, it is the pulmonary acinus that play a signifigant role in the lung disease prevention, treatment and inhalation therapy development.At present, due to the physiological structure of the human pulmonary acinus parts with small scal(micron),alveolar number(3-4 billion) and the complicated structure, the experiment(CT scan) is difficult to detect the detailed structure. In addition, the change of the alveolar also increases the difficulty of numerical simulation. Based on the the structure of human pulmonary and respiratory physiology, the whole pulmonary acinus 3D model are established with assumptions and simplifications.Euler and Lagrange methods are chosed to simulate the airflow pattern and particle deposition respectively.The N-S equations and Newton second law are taken as the control equations. The multiphysics numerical simulation software COMSOL is used to analyse and study airflow patterns and the deposition of particle under three unsteady breathing scenarios. The effects of respiratory and pulmonary acinus series on the flow field and the particle size, density and the respiratory cycle on particle deposition is analysed.The results show that simulation of ventilation is the same order of real ventilation, and pulmonary pressure drop decreases with the increase of pulmonary acinus series. By comparing streamlines at each generation of the pulmonary acinus, the state was observed that alveolar flows are dominated by recirculating flows in the proximal acinar generations and radial flows in the deeper acinar generations. The particle deposition rate increases with the particle size increasing; Gravity settling dominant the particle deposition of 1-3μm, and the influence on 0.05-0.5μm can be neglected. The particle deposition rate of 1-3μm increases with the density increasing linearly. When lengthening the statistical time, global deposition efficiency is increasing except 0.05,0.1and3 micron particle.The particle deposition rate of three-dimensional model is higher than that of the two-dimensional model.By comparing the growth rate of deposition, it is found that the effect of the three dimensional model to large particle is larger than that the small particle.