| Aortic Dissection(AD)is a disease of aortic endovascular blood flowing through the intimal tear of the aortic wall into the outer layer of the aortic inner membrane or the border between the outer membrane and the medial outer membrane.It has the characteristics that the false cavity is easy to break,and the damage is easy to die.Through the combination of medical imaging technology and Computational Fluid Dynamics(CFD),numerical simulation of aortic dissection blood flow and analysis of hemodynamic behavior are of great significance for clinical judgement and disease prevention and treatment.The multiphase flow method to simulate the flow of blood in aortic dissection is a new achievement in the application of computational fluid mechanics to medicine both at home and abroad.Basing on a case of De Bakey III aortic dissection,the flowing blood in the aortic dissection was simulated numerically to explore the hemodynamic behavior in aortic dissection.This paper tries to explain the causes and the location of breakage from a mechanical perspective,explain the cause and harm of aortic dissection rupture from the perspective of red blood cells,compare the motion state of various solid substances in the blood,and finally put forward some suggestions for treatment.The results of the study provide a useful reference for the prevention and treatment of aortic dissection,which is of clinical significance.The main contents of this paper are as follows:Firstly,the basic information of aortic dissection is introduced,including the definition,classification harm and main treatment of aortic dissection.According to the information,the main research direction and clinical significance of this paper are introduced,and the advantages of selecting multiphase flow simulation and the necessity of using large-scale computing are explained.Secondly,The process of transforming tomographic images into computational models for patients with De Bakey III aortic dissection is introduced,including three parts:geometric modeling,mesh generation and boundary setting.It lays the foundation for the efficiency and convergence of the calculation.Thirdly,Lagrange's multiphase flow dynamic control equation and numerical calculation method are introduced.The numerical calculation model,physical parameters,model selection and time step setting of aortic dissection are expounded.These lay the foundation for the reasonable and reliable results.Fourthly,the Lagrange multiphase flow method was used to simulate the flow of aortic dissection and to analyze the hemodynamic behavior.The study found that laminar flow is easy to appear in the heart fire blood and vortex is easy to appear in diastole.The low velocity vortex is easy to appear at the proximal end of the false cavity,and the high-speed vortex is easy to appear near the re break of the abdominal artery.There are high pressure and high wall shear stress in the false lumen of the proximal end,which lead to vascular wall injury and rupture easily;The dissection of the aorta has a hindrance to the flow of blood and causes insufficient blood supply in the organs.Fifthly,the Lagrange multiphase flow model was used to simulate the blood movement in the dissection of the aorta.The red cell volume fraction maps were drawn at four typical times.The Red blood cell trajectory time and velocity maps were drawn in four typical periods.The study explored the movement of erythrocyte in the aortic dissection,and explained the cause and harm of the aortic dissection rupture from the angle of red cell movement.It was found that the change of erythrocyte velocity was lagging behind the change of blood velocity.It is found that red cell aggregation is easy to occur at the proximal end of the false cavity,and the thrombus is easily generated in this position.It was found that the proximal end of the false cavity had less contact with the fresh blood,which hindered the self repair of the vascular wall.It was found that the dissection of the aorta hinders the passing of red blood cells and further reduces the ability of blood to carry red blood cells on the basis of obstructing blood flow and aggravates the lack of blood supply.Sixthly,three kinds of particle size solids were added to the blood,and their diameters are 7 × 10-6m,7 × 10-71m and 7 × 10-8m.The blood flow of aortic dissection containing three kinds of solid phase was simulated.Based on the motion trajectories of three solid phases,velocity and temporal cloud images were established to compare the motion rules of three solid phases in aortic dissection.It was found that the distribution rule of three solid phase was closely related to the motion rule.The movement of solid phases of 7 × 10-8m diameter is agile,and affected quickly by the blood,so it can be with the blood in the false lumen repeated movement.The movement of solid phases of 7 × 10-6m diameter is affected hard by the blood,and easy to flow out of the aortic dissection after being speeded up in long straight passages.Similarly,because of this characteristic,it is not easy to be carried away by blood,so it is more likely to exist in the proximal part of the false cavities.Solid phases of 7 × 10-7m stays at the least at the proximal end of the false cavity and stays most in the abdominal artery.There are many different functions of solid particles in the blood.They come from themselves or come from the injection.The particle distribution information can be obtained by distinguishing the particle size.This information can guide the medical means to regulate the particle concentration in the specific position of the body.The prevention and treatment of the aortic dissection can be more targeted by controlling the usefulness of the particles in a specific position or reducing their harmful effects. |
PDF Full Text Request