Department of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran.
Department of Mechanical Engineering, University of Birjand, Birjand, Iran.
Comput Methods Programs Biomed. 2018 Feb;154:109-122. doi: 10.1016/j.cmpb.2017.11.016. Epub 2017 Nov 15.
In this study, the interaction of pulsatile blood flow with the viscoelastic walls of the axisymmetric artery is numerically investigated for different severities of stenosis. The geometry of artery is modeled by an axisymmetric cylindrical tube with a symmetric stenosis in a two-dimensional case. The effects of stenosis severity on the axial velocity profile, pressure distribution, streamlines, wall shear stress, and wall radial displacement for the viscoelastic artery are also compared to the elastics artery. Furthermore, the effects of atherosclerosis and polycythemia diseases on the hemodynamics and the mechanical behavior of arterial walls are investigated.
The pulsatile flow of non-Newtonian blood is simulated inside the viscoelastic artery using the COMSOL Multiphysics software (version 5) and by employing the fluid-structure interaction (FSI) method and the arbitrary Lagrangian-Eulerian (ALE) method. Moreover, finite element method (FEM) is used to solve the governing equations on the unstructured grids. For modeling the non-Newtonian blood fluid and the viscoelastic arterial wall, the modified Casson model, and generalized Maxwell model are used, respectively.
According to the results, with stenosis severity increasing from 25% to 75% at the time of maximum volumetric flow rate, the maximum value of axial velocity and its gradient increase 7.9 and 19.6 times, and the maximum wall shear stress of viscoelastic wall increases 24.2 times in the constriction zone. With the progression of the atherosclerosis disease (fivefold growth of arterial elastic modulus), the wall radial displacement of viscoelastic arterial walls decreases nearly 40%.
In this study, axial velocity profile, pressure distribution, streamlines, wall radial displacement, and wall shear stress were examined for different percentages of stenosis (25%, 50%, and 75%). The atherosclerosis disease was investigated by the fivefold growth of viscoelastic arterial elastic modulus and polycythemia disease was examined by the 21-fold increase in the yield stress of the blood fluid. Furthermore, the comparison of results between the elastic and viscoelastic arterial walls shows that the wall radial displacement for viscoelastic artery is lower than that for the elastic artery as much as 21.7% for the severe stenosis of 75%.
本研究旨在数值研究不同狭窄程度下脉动血流与轴对称动脉粘弹性壁之间的相互作用。在二维情况下，通过轴对称圆柱形管模拟动脉的几何形状，其中存在对称狭窄。还将比较弹性和粘弹性动脉的狭窄严重程度对轴向速度分布、压力分布、流线、壁切应力和壁径向位移的影响。此外，还研究了动脉粥样硬化和红细胞增多症等疾病对动脉血流动力学和壁力学行为的影响。
使用 COMSOL Multiphysics 软件（版本 5）通过使用流固耦合（FSI）方法和任意拉格朗日-欧拉（ALE）方法模拟粘弹性动脉内的非牛顿血液脉动流。此外，使用有限元法（FEM）在非结构化网格上求解控制方程。为了模拟非牛顿血液流体和粘弹性动脉壁，分别使用修正的 Casson 模型和广义 Maxwell 模型。
结果表明，在最大容积流量时，狭窄严重程度从 25%增加到 75%，在狭窄区域，轴向速度最大值及其梯度增加了 7.9 倍和 19.6 倍，粘弹性壁的最大壁切应力增加了 24.2 倍。随着动脉粥样硬化疾病（动脉弹性模量增加五倍）的发展，粘弹性动脉壁的壁径向位移减少了近 40%。
在这项研究中，检查了不同狭窄百分比（25%、50%和 75%）的轴向速度分布、压力分布、流线、壁径向位移和壁切应力。通过将粘弹性动脉弹性模量增加五倍研究了动脉粥样硬化疾病，通过将血液屈服应力增加 21 倍研究了红细胞增多症疾病。此外，弹性和粘弹性动脉壁之间的结果比较表明，在严重狭窄（75%）时，粘弹性动脉的壁径向位移比弹性动脉低 21.7%。
