Chen Jie, Lu Xi-Yun
Department of Modern Mechanics, University of Science and Technology of China, 96 Jin-Zhai Road, Hefei, Anhui 230026, PR China.
J Biomech. 2006;39(5):818-32. doi: 10.1016/j.jbiomech.2005.02.003.
The pulsatile flow of non-Newtonian fluid in a bifurcation model with a non-planar daughter branch is investigated numerically by using the Carreau-Yasuda model to take into account the shear thinning behavior of the analog blood fluid. The objective of this study is to deal with the influence of the non-Newtonian property of fluid and of out-of-plane curvature in the non-planar daughter vessel on wall shear stress (WSS), oscillatory shear index (OSI), and flow phenomena during the pulse cycle. The non-Newtonian property in the daughter vessels induces a flattened axial velocity profile due to its shear thinning behavior. The non-planarity deflects flow from the inner wall of the vessel to the outer wall and changes the distribution of WSS along the vessel, in particular in systole phase. Downstream of the bifurcation, the velocity profiles are shifted toward the flow divider, and low WSS and high shear stress temporal oscillations characterized by OSI occur on the outer wall region of the daughter vessels close to the bifurcation. Secondary motions become stronger with the addition of the out-of-plane curvature induced by the bending of the vessel, and the secondary flow patterns swirl along the non-planar daughter vessel. A significant difference between the non-Newtonian and the Newtonian pulsatile flow is revealed during the pulse cycle; however, reasonable agreement between the non-Newtonian and the rescaled Newtonian flow is found. Calculated results for the pulsatile flow support the view that the non-planarity of blood vessels and the non-Newtonian properties of blood are an important factor in hemodynamics and may play a significant role in vascular biology and pathophysiology.
利用Carreau-Yasuda模型考虑模拟血液流体的剪切变稀行为，对具有非平面分支的分叉模型中牛顿流体的脉动流进行了数值研究。本研究的目的是探讨流体的非牛顿特性以及非平面分支血管中的平面外曲率对壁面剪应力（WSS）、振荡剪切指数（OSI）和脉搏周期内流动现象的影响。分支血管中的非牛顿特性由于其剪切变稀行为导致轴向速度分布变平。非平面性使血流从血管内壁偏向外壁，并改变了沿血管的WSS分布，特别是在收缩期。在分叉下游，速度分布向分流器移动，在靠近分叉的分支血管外壁区域出现以OSI为特征的低WSS和高剪应力时间振荡。随着血管弯曲引起的平面外曲率的增加，二次运动变得更强，二次流模式沿非平面分支血管涡旋。在脉搏周期中揭示了非牛顿脉动流和牛顿脉动流之间的显著差异；然而，发现非牛顿流和重新缩放的牛顿流之间有合理的一致性。脉动流的计算结果支持这样的观点，即血管的非平面性和血液的非牛顿特性是血液动力学中的一个重要因素，可能在血管生物学和病理生理学中起重要作用。
