【作者】 王家权；

【导师】 伍时桂；

【作者基本信息】 北京工业大学 ， 流体力学， 2002， 博士

【摘要】 越来越多的研究证据表明，血流动力学因素在动脉粥样硬化的发生和发展过程中起着关键的作用。但时至今日血流动力学因素确切的作用还需要进一步了解，因此更深入地研究动脉粥样硬化的生物力学机理对于掌握动脉粥样硬化的病理和发病规律有着巨大的研究价值。 近年来，随着人们生活水平的不断提高和生活结构的逐步改变，心血管病的发病率也在不断增加，并已经成为危害人类生命健康最为严重的疾病之一，其患病率和死亡率居各类疾病之首，因而成为发达国家和发展中国家的头号杀手。它所造成的死亡率占所有疾病死亡率的百分之二十五。世界卫生组织已把它列为当今危害人类健康的三大疾病之一。调查结果表明，发达国家中大约有百分之五十五的人在年轻时冠状动脉中就已开始出现脂肪纹和纤维斑，这是心血管疾病的最初表现。动脉粥样硬化作为常见的心血管疾病，其致病的成因和发展的机制一直是生物医学工程领域研究的热门课题之一。由此可见，对于心血管疾病的防治，发现并掌握心血管疾病的发病规律，完善检测手段和治疗措施已成为当前世界医学界所面对的重要课题。 本文的着眼点和研究的目的在于，希望利用在血流动力学方面的研究优势，用有限元方法对动脉粥样硬化的血流动力学问题进行数值模拟，研究动脉粥样硬化在生成和发展过程中的血流动力学、血管壁生理及生物力学性能的变化规律，以及这两种变化规律之间的相互作用与动脉粥样硬化的发生和发展的关系，通过大量算例的对比分析，以期在这方面作些基础而有实际价值的工作。 本课题研究的意义还在于，对动脉硬化进行生物流体力学、生物固体力学、医学及计算流体力学等多学科的综合研究，弥补纯生化研究的不足，全面反映动脉硬化的发病机制及发展规律，为动脉硬化的预防和治疗提供有益的理论基础。因此，本项目有着良好的应用前景，它不仅可以提供动脉粥样硬化形成和发展的血流动力学机理，而且可以形成动脉粥样硬化血流动力学参数的检测和分析方法，可进一步应用于动脉粥样硬化的临床诊断。 北京工业大学工学博士学位论文一 在研究中借鉴了同行研究者血管分岔形态的忧化分析的研究结果。研究认 为血管作为人体的组织器官，是几十亿年的生物进化的结果。近20年来，人们 普遍接受的原理主要有：最小能耗原理：最小阻抗原理；最小容量原理。这些 原理在分析问题时或多或少地用到了泊肃叶定理。 在研究中血液被看作是牛顿流体，流动是充分发展的轴对称层流，故遵循 泊肃叶定律。实际生理条件下，血液是粘弹性流体，但据文献表明，只要血管 直径不太小，血液粘弹性对流动的影响不大，可以忽略不记，本文也吸收了这 一结论以简化非关键过程，以提高工作效率。 冠状动脉粥样硬化主要的病理症状主要发生在弯曲、分岔和狭窄等多因素 复合的情况下，因此多因素复合模型是目前这一研究领域的发展方向。为了更 接近于实际生理条件，本文通过建立了空间三维的二级冠状动脉的几何模型和 数学模型，对生理条件下的弯曲、狭窄和分岔管路条件下的流场进行了大量的 计算模拟。这些计算包括：脉动流情况下的非狭窄和狭窄不对称性对狭窄流场 的影响，分岔角度变化时动脉狭窄和非狭窄的各种血流动力学参数的计算模拟。 本文的计算模拟工作采用了工程计算中高效可靠、认知度比较高的ANSYS 计算软件来进行，ANSYS软件的通用型和精确度也被业内人土广为认同。因此， 在建立几何精确建模和方程求解上可以节省相当的时间和精力，并能使一部分 工作得到简化，所以能够克服通常编程时一些细节上的烦杂，将主要精力放到 计算结果的后处理和结果的分析上，以便为；临床提供更多有价值的结果。 为了研究多因素复合情况下的冠状动脉血流动力学情况，本文构造的分岔 模型是可变角度的通用模型和计算程序，其分岔角度可以在 0”一 180“之间任意 设置。这对于研究分岔对病变的影响提供的很多方便。 为了突出研究重点，本文的主要工作集中在人们最为关注的流场与剪应力 的模拟求解、分析处理上，而对于速度和二次流的结果也一并得出。本文的计 算模拟的结果与己有的计算与临床实验结果有着很好的吻合。更多还原

【Abstract】 There is more and more evidence that hemodynamic factors play an important role in the development of the arterial atherogenesis, but even up to now, the specific role of the hemodynamic factors is not well understood yet, therefore further research work of revealing the biomechanical mechanism of atherosclerosis is helpful and necessary to learn its pathology and occurrence, which is very important in biofluid dynamics and is closely related to the development of the biofluid dynamics in theory and numerical simulation, the investigation of coronary circulation rules of human cardiovascular system and the further study of occurrence mechanism of cardiovascular diseases, so is of great significance in both scientific research work and realistic application.To study the effect of the hemodynamic factors on the atherogenesis, a series of spatial 3D asymmetric geometric models of coronary artery were built up in this paper. By FEM, the numerical simulation was carried out according to such models, many important hemodynamic variables, such as the tempo-spatial velocity field at every cross section of the artery, the pressure distribution, the secondary flow and the WSS (wall shear stress) at the specific areas were obtained, which will help understand the biomechanics of coronary atherosclerosis furtherly.Many investigators studied the stenotic artery by means of 2 dimensional models, which can only simulate the planar pulsatile waves and got, to some extent, some general results of the blood flow without considering the secondary flow and the reality of physiological conditions. In this paper, 3D spatial asymmetric conditions and real physiological conditions were introduced both in the geometric models and the biomechanical models. The stenosis degree and the bifurcation angel can vary at will according to any requirements specified, the universal program was set up, which can be developed into an individual oriented, real-time and clinically practicalprogram to provide more valuable reference for the surgeon in the clinical diagnosis and disease prediction.To construct geometric models, the main stem and the branches of coronary artery are assumed to develop along the surface of a sphere which simulates a heart body so as to obtain more accurate spatial 3D asymmetric descriptive models for the simulation of the coronary artery. By this method, 3 generations of the coronary branches can be got to simulate more accurate models of coronary vasculature. For simplicity, these assumptions are followed in the simulation :1) The coronary artery is modeled as rigid tube with constant cross section;2) the blood is assumed as viscous incompressible Newtonian fluid without weight;3) the blood flow is developing laminar and becomes fully developed at far downstream.To simulate the nonlinear pulsatile waves propagating in coronary artery, transient analysis was utilized in numerical simulation. One cardiac cycle is divided into 50 parts in the transient analysis to accurately simulate the continuous pulsatile blood flow in the coronary artery, the hemodynamic parameters of the atherosclerotic and the controlled models at each of the 50 moments were computed in accordance with the physiological condition.Compared with the observed result in clinical experience, atheroma often occurs at the place where the WSS is greater and less, this experience is corroborated by the result obtained in the numerical simulation, that is to say, where the higher or the lower the WSS is, where it is more possible for atherosclerosis to take place. The peak values of the WSS appear at the edge of the bifurcation, so the patients should be on the stick for preventing the development of the atherogenesis.Many computational results were obtained and can provide the inner hemodynamic situation at each moment of the cardiac cycle and each specified position of the coronary bifurcation for learning the severity of the atherosclerosis in the coronary artery. The hemodynamical variables and the visible flow conditio更多还原