Finite Element Analysis And Computational Fluid Dynamics Simulation In Human Large Artery

Atherosclerosis is a chronic and progressive inflammatory disease of the arterial wall, particularly in the middle and large arteries, it is responsible for two thirds of all deaths. Atherogenesis is known to be associated with the Hemodynamic factors, the regions of arterial branching and curvature are associated with complex blood flow patterns, it has been accepted that blood flow may play an important role in atherogenesis.The Hemodynamic factors play a very important role in the initiation and progression of atherosclerosis. Hemodynamic disturbances have been strongly related to the localization of atherosclerotic lesions on the vessel walls. Some works had shown that lesions occur in regions of high wall shear stress(WSS),and the arterial endothelium is damaged by the high WSS. However, some studies which had a work of human post-mortem specimen suggested that lesions always occur in regions of low wall shear rate(WSR). The theory of low wall shear rate is widely accepted today.In recent years, mathematical models of the vascular system have been extensively used to simulate arterial hemodynamics in both healthy and pathological conditions. The advent and development of high speed computers has increased the scope for applications of mathematical and computational methods in solving Hemodynamic problems.In this paper, we mainly elaborated the process of finite element computer simulation which was used in the study of human arteries fluid mechanics, including the research methods, model building, the set of research conditions, results analysis, clinical significance and so on. This can make the experimental method and model building more optimized, make the research more close to the physiological state, increase the effectiveness of the results,improve the theoretical basis for clinical research, and provide methods for follow-up studies.Part one Finite Element Analysis of Pulsatile Blood Flow in RealisticViscoelastic Arterial Wall Model: Study of Coronary arteryObjective: To observe the hemodynamic characteristics of Different degree stenosis in left coronary artery under pulsating flow; the contrast of hemodynamic parameters is obtained at different observation points; the contrast and changes of hemodynamic parameters were also obtained at prestenotic artery, stenosis and poststenotic artery.Methods: Selecting each case from Ⅰ °- Ⅳ °typical coronary stenosis cases, and then the CTA data was obtained by using the GE multiplies spiral CT. The CTA data is stored into the read-write CD-ROM in DICOM files.Models ofⅠ °- Ⅳ ° coronary stenosis were established with MIMICS14.0software, and then optimized the three-dimensional model in Geomagic9.0software and form the fedb documents. Then the model file was imported into Workbench 13.0 to build flow-solid coupling procedures, and performed meshing and settings on the wall and blood for coupling calculation and analysis.Results:1. Models ofⅠ °- Ⅳ ° coronary stenosis were established with the software MIMICS14.0.2. The fedb document was established by the software Geomagic9.0.3. Finite Element Models ofⅠ °- Ⅳ ° coronary stenosis were established with the software ANSYS Workbench14.0.4. A series of computational fluid visualized data ofⅠ °- Ⅳ ° coronary stenosis was got, about the point1,point2 and point3. Changes of the fluid dynamics in different areas of the narrow blood vessels was Analyzed.5. Streamlines of Ⅰ °- Ⅳ ° coronary stenosis were got at the time0.15 s,0.25 s,0.35 s,0.45 s.6. Velocity of Ⅰ °- Ⅳ ° coronary stenosis was got at the time 0.15 s,0.25 s, 0.35 s, and 0.45 s. The calculated result showed that the velocity was increased in the vessel, and the velocity in prestenotic artery was lower than that in poststenotic artery.7. Pressure of Ⅰ °- Ⅳ ° coronary stenosis was got at the time 0.15 s,0.25 s, 0.35 s, and 0.45 s.8. WSS of Ⅰ °- Ⅳ ° coronary stenosis was got at the time 0.15 s, 0.25 s,0.35 s, and 0.45 s. The highest WSS appeared at the stenosis, and the WSS decreased in poststenotic artery.9. Wall deformation of Ⅰ °- Ⅳ ° coronary stenosis was got at the time0.15 s, 0.25 s, 0.35 s, and 0.45 s.10. Pressure of Ⅰ °- Ⅳ ° coronary stenosis was got at observation points.11. WSS of Ⅰ °- Ⅳ ° coronary stenosis was got at observation points.12. The contrast of pressure changes were obtained at prestenotic artery,stenosis and poststenotic artery.13. The contrast of WSS changes were obtained at prestenotic artery,stenosis and poststenotic artery.14. Pressure and velocity of coronary stenosis was got at cross-sectional.15. Pressure and velocity of coronary stenosis was got at poststenotic area.16. Pressure and velocity of coronary stenosis was got at coronary plane.Conclusion: The hemodynamic changes of the coronary artery had a close relationship with AS. The higher the degree of vascular stenosis, the more important the hemodynamic factors played a role in the AS, the faster the AS development. This could explain that why the AS progression of patients is getting faster and faster, and provide the theoretic foundation for clinical early intervention.Part two Finite Element Analysis of Human Carotid Artery Bifurcationwith a Viscoelastic Arterial Wall Fluid-solid Coupling ModelObjective: To investigate the role of Geometry and WSS in the hemodynamics changes, the variation of WSS and wall deformation under different pressures. To discuss the role of WSS changes played in the progression of AS.Methods: Selecting one case from typical carotid artery CTA scan cases,and the CTA data was obtained by using the GE multiplies spiral CT. The CTA data is stored into the read-write CD-ROM in DICOM files. A model of carotid artery bifurcation was established with MIMICS14.0 software, and then optimized the three-dimensional model in Geomagic9.0 software and forms the fedb documents. Then the model file was imported into Workbench13.0 to build flow-solid coupling procedures, and performed meshing and settings on the wall and blood for coupling calculation and analysis.Results:1 The data of normal carotid bifurcation was obtained.2 The 3 d model of normal carotid bifurcation was established.3 The finite element model of normal carotid bifurcation was established.4 Streamlines distributions of normal carotid bifurcation were got at different time.5 Velocity distributions of normal carotid bifurcation were got at different time.6 Pressure distributions of normal carotid bifurcation were got at different time.7 WSS distributions of normal carotid bifurcation were got at different time.8 Wall deformation distributions of normal carotid bifurcation were got at different time.9 Pressure and WSS distributions of normal carotid bifurcation were got at observation points.10 Pressure, velocity and WSS distributions of normal carotid bifurcation were got at 0.3s under three different pressures.11 The contrast of pressure and WSS distributions were obtained at observation points under 1200 Pa, 1600 Pa and1900Pa. The contrast tables of pressure and WSS changes were also obtained at observation points under different pressure.12 Velocity distributions of carotid bifurcation and sinus were got at cross-sectional.13 Velocity of carotid bifurcation was got at coronary plane.Conclusion: The hemodynamic changes of high pressures and geometry had a close relationship with AS. Carotid sinus and bifurcation were the mostly affected areas by hemodynamics. They were also the the predilection site of AS according to early researchs. That was consistent with clinical conditions, and could explain that why the hypertensive patients were vulnerable to AS.Part three Computational fluid dynamics simulation and analysis of theLower limb artery stenosisObjective: To observe the hemodynamic characteristics of Lower limb artery stenosis under pulsating flow. To discuss the role of dynamic parameters played in the progression of AS.Methods: Selecting one case from typical lower limb artery CTA scan cases, and the CTA data was obtained by using the GE multiplies spiral CT.The CTA data is stored into the read-write CD-ROM in DICOM files. Models of carotid artery bifurcation were established with MIMICS14.0 software, and then optimized the three-dimensional model in Geomagic9.0 software and form the fedb documents. Then the model file was imported into Workbench13.0 to build flow-solid coupling procedures, and performed meshing and settings on the wall and blood for coupling calculation and analysis.Results:1. The 3 d model of lower limb artery was established.3. The finite element model of lower limb artery was established.4. Streamlines distributions of lower limb artery were got at different time. Streamline distribution was uniform, displayed as laminar flow; the change of velocity was not big, the streamline was intensive at the narrow area.5. Velocity distributions of lower limb artery were got at different time.Velocity increased significantly at the stenosis, and the vascular endothelial cell could be damaged by the high speed flow. The velocity decreased at areas away from the stenosis.6. Pressure distributions of lower limb artery were got at different time.Pressure decreased significantly at the stenosis, and formed pressure gradient at the stenosis and near it.7. WSS distributions of lower limb artery were got at different time. WSS increased significantly at the stenosis and decreased greatly away from the stenosis. That could form obviously gradient.8. Wall deformation distributions of lower limb artery were got at different time. Wall deformation was most significant at the stenosis.Conclusion: The geometry of the artery had a close relationship with AS,the AS more often occurred in the stenosis.The AS plaque would gradually increase and block the lumen unless intervention measures. The hemodynamic factors played important roles in the progress of the plaque, so we should know the characters of the hemodynamic.The finite element numerical simulation is the best mechanics research method of arterial blood flow currently. We could obtain more meaningful parameters by further study and using it skillfully, help clinicians make treatments.