European Centre of Excellence NTIS - New Technologies for Information Society, Faculty of Applied Sciences, University of West Bohemia, Pilsen, Czech Republic.
Int J Numer Method Biomed Eng. 2013 Oct;29(10):1057-81. doi: 10.1002/cnm.2560. Epub 2013 Jun 4.
Considering the fact that hemodynamics plays an important role in the patency and overall performance of implanted bypass grafts, this work presents a numerical investigation of pulsatile non-Newtonian blood flow in three different patient-specific aorto-coronary bypasses. The three bypass models are distinguished from each other by the number of distal side-to-side and end-to-side anastomoses and denoted as single, double and triple bypasses. The mathematical model in the form of time-dependent nonlinear system of incompressible Navier-Stokes equations is coupled with the Carreau-Yasuda model describing the shear-thinning property of human blood and numerically solved using the principle of the SIMPLE algorithm and cell-centred finite volume method formulated for hybrid unstructured tetrahedral grids. The numerical results computed for non-Newtonian and Newtonian blood flow in the three aorto-coronary bypasses are compared and analysed with emphasis placed on the distribution of cycle-averaged wall shear stress and oscillatory shear index. As shown in this study, the non-Newtonian blood flow in all of the considered bypass models does not significantly differ from the Newtonian one. Our observations further suggest that, especially in the case of sequential grafts, the resulting flow field and shear stimulation are strongly influenced by the diameter of the vessels involved in the bypassing.
鉴于血液动力学在植入旁路移植物的通畅性和整体性能中起着重要作用，本工作对三种不同的患者特定主动脉冠状动脉旁路中的脉动非牛顿血流进行了数值研究。三种旁路模型通过远端侧侧和端端吻合术的数量来区分，分别表示为单、双和三旁路。以时变非线性不可压缩纳维-斯托克斯方程系统的形式表示的数学模型与描述人血剪切稀化特性的 Carreau-Yasuda 模型相结合，并使用 SIMPLE 算法原理和针对混合非结构四面体网格的单元中心有限体积方法进行数值求解。在三种主动脉冠状动脉旁路中计算的非牛顿和牛顿血流的数值结果进行了比较和分析，重点放在循环平均壁面剪切应力和振荡剪切指数的分布上。正如本研究所示，所有考虑的旁路模型中的非牛顿血流与牛顿血流没有显著差异。我们的观察结果进一步表明，特别是在连续移植物的情况下，旁路中涉及的血管的直径强烈影响到血流场和剪切刺激。
