Lee K W, Xu X Y
Department of Chemical Engineering & Chemical Technology, Imperial College of Science, Technology and Medicine, SW7 2BY, London, UK.
Med Eng Phys. 2002 Nov;24(9):575-86. doi: 10.1016/s1350-4533(02)00048-6.
In the present computational analysis, pulsatile flow and vessel wall behaviour in a simplified model of a stenosed vessel were investigated. Geometry of a 45% axisymmetrically stenosed (by area) cylindrical tube and a sinusoidal inflow waveform were simulated, with the fluid being assumed to be incompressible and Newtonian. The vessel wall was treated as a thick-walled, incompressible and isotropic material with uniform mechanical properties across the normal as well as the constricted segment. The study of fluid flow and wall motion was initially carried out separately using two commercial codes CFX4.2 and ABAQUS7 respectively. Their combined effects and interactions were later investigated through an iteratively coupled algorithm. Model validations on the rigid-wall fluid and static no-flow solid models were satisfactory, with Root Mean Square deviations of around 7% in centreline axial velocity between the prediction and measurement values for the rigid wall stenosis model, and 5% in circumferential stress for a cylindrical tube model under static loading when compared with the analytical solution. Results on velocity profiles, wall shear stress, intramural strain and stress for the rigid and compliant cases were all presented. Comparison between the rigid and compliant models revealed that, the flow separation layer distal to the stenosis was thicker and longer, and wall shear stress was slightly lower in the compliant model by less than 7.2%. Results obtained from the static wall model (with uniform pressure loading) and coupled fluid/wall interaction modelling of pulsatile flow showed qualitatively similar wall strain and stress patterns but considerable differences in magnitude. The radial and axial stresses were reduced by 31 and 8%, while the circumferential stress was increased by 13% due to the presence of pulsatile flow. Under the flow and structural conditions investigated, the effects of wall compliance were small, and did not change the flow and solid behaviours qualitatively in this case.
在当前的计算分析中，研究了狭窄血管简化模型中的脉动流和血管壁行为。模拟了一个面积轴对称狭窄45%的圆柱形管的几何形状和正弦流入波形，假设流体为不可压缩牛顿流体。血管壁被视为厚壁、不可压缩且各向同性的材料，在法线方向以及收缩段具有均匀的力学性能。最初分别使用两个商业代码CFX4.2和ABAQUS7对流体流动和壁运动进行了研究。后来通过迭代耦合算法研究了它们的综合影响和相互作用。对刚性壁流体模型和静态无流固体模型的模型验证结果令人满意，刚性壁狭窄模型的预测值与测量值之间的中心线轴向速度的均方根偏差约为7%，与解析解相比，静态加载下圆柱形管模型的周向应力偏差为5%。给出了刚性和柔性情况下的速度剖面、壁面剪应力、壁内应变和应力的结果。刚性模型和柔性模型的比较表明，狭窄远端的流动分离层更厚更长，柔性模型中的壁面剪应力略低，降幅小于7.2%。从静态壁模型（均匀压力加载）和脉动流的流体/壁面相互作用耦合建模获得的结果在壁应变和应力模式上定性相似，但在量级上有很大差异。由于存在脉动流，径向和轴向应力分别降低了31%和8%，而周向应力增加了13%。在所研究的流动和结构条件下，壁面柔性的影响较小，在这种情况下没有定性地改变流动和固体行为。
