Characteristics Of Airflows In COPD Airways By Computational Fluid Dynamics

Chronic obstructive pulmonary disease(COPD)is a kind of lung disease with the most significant future of airflow limitation.In recent years,it become more and more common.It is characterized by high morbidity rates,supernal mortality and poor therapy effect which have brought great economic burden for patients and their families..Pulmonary function tests have been used clinically to obtain some parameters of lung airway,but there are also some mechanical parameters shortcomings in gaining gas velocity of human airway,wall shear stresses and the flow distribution of the all levels bronchus.This thesis aims at investigating the differences of airway between patients and normal persons.We also reveal the pathogenesis of COPO in viewpoint of morphology,physics and mathematics.This paper introduces computed fluid dynamics(CFD)technology to research the gas flow characteristics in human airway,and we use the continuous and complete CT image to build three-dimensional geometry models of human airway with Mimics software based on CT scanning technology.Next,We translate geometry models into X_t-formatted files and then import the projects in ANSYS Workbench simulate the system exactly.In this paper we select four COPD patients and a normal person acted as controls,and we assume that airway walls was rigid wall and air was Newtonian gas.Combined with personalized respiratory parameters.In order to get the relevant parameters which can reflect the air flow characteristics in the trachea,we use velocity inlet boundary conditions,pressure outlet boundary conditions,and standard k-? turbulence models.The simulation results include air flow velocity,wall pressure,wall shear stress,the moving direction of the airway,flow distribution.Following results were obtained by studying the parameters.The main results include:(1)Compared with healthy subjects A,the airway of patients with COPD have deformation(2)Compared with healthy subjects A,for patients with COPD,the pressure drop is far higher than the normal control subjects.The airway pressure drop for normal subjects is 2.20Pa,and pressure drop for the patients with COPD,the pressure drop is 14.2Pa,21.9Pa,17.89Pa,27.31Pa,more higher than the healthy contral subjects.(3)Compared with normal control subjects A,the distribution of velocity,wall pressure and wall shear stress in the airways for COPD patients is more uneven.(4)Compared with healthy subjects A,for patients with COPD,the narrow zone of airways have a higher velocity,lower wall pressure,higher wall shear stress.(5)Compared with healthy subjects A,for patients with COPD,the maximum wall pressure appeared at the entrance.(6)For five subjects,The area ratio of the right outlet is 0.638,0.57,0.614,0.702,0.606,and the flow ratio is 0.7,0.609,0.612,0.763,0.643.According to the data we can concluded that the outlet area ratio is associated with flow ratio,the correlation coefficient is 0.99.