Leble Vladimir, Lima Rui, Dias Ricardo, Fernandes Carla, Ishikawa Takuji, Imai Yohsuke, Yamaguchi Takami
Biomicrofluidics. 2011 Dec;5(4):44120-4412015. doi: 10.1063/1.3672689. Epub 2011 Dec 23.
In microcirculation, red blood cells (RBCs) flowing through bifurcations may deform considerably due to combination of different phenomena that happen at the micro-scale level, such as: attraction effect, high shear, and extensional stress, all of which may influence the rheological properties and flow behavior of blood. Thus, it is important to investigate in detail the behavior of blood flow occurring at both bifurcations and confluences. In the present paper, by using a micro-PTV system, we investigated the variations of velocity profiles of two working fluids flowing through diverging and converging bifurcations, human red blood cells suspended in dextran 40 with about 14% of hematocrit level (14 Hct) and pure water seeded with fluorescent trace particles. All the measurements were performed in the center plane of rectangular microchannels using a constant flow rate of about 3.0 × 10(-12) m(3)/s. Moreover, the experimental data was compared with numerical results obtained for Newtonian incompressible fluid. The behavior of RBCs was asymmetric at the divergent and convergent side of the geometry, whereas the velocities of tracer particles suspended in pure water were symmetric and well described by numerical simulation. The formation of a red cell-depleted zone immediately downstream of the apex of the converging bifurcation was observed and its effect on velocity profiles of RBCs flow has been investigated. Conversely, a cell-depleted region was not formed around the apex of the diverging bifurcation and as a result the adhesion of RBCs to the wall surface was enhanced in this region.
在微循环中，流经分叉处的红细胞（RBCs）可能会因微观尺度上发生的不同现象的综合作用而发生显著变形，这些现象包括：吸引效应、高剪切力和拉伸应力，所有这些都可能影响血液的流变特性和流动行为。因此，详细研究分叉处和汇合处发生的血流行为非常重要。在本文中，我们使用微观粒子图像测速（PTV）系统，研究了两种工作流体流经发散和汇聚分叉处时速度分布的变化，一种是悬浮在右旋糖酐40中、血细胞比容水平约为14%（14 Hct）的人红细胞，另一种是含有荧光示踪颗粒的纯水。所有测量均在矩形微通道的中心平面上进行，流速约为恒定值3.0×10⁻¹² m³/s。此外，将实验数据与牛顿不可压缩流体的数值结果进行了比较。红细胞在几何形状的发散侧和汇聚侧的行为是不对称的，而悬浮在纯水中的示踪颗粒的速度是对称且能被数值模拟很好地描述。观察到在汇聚分叉顶点下游立即形成了一个红细胞贫化区，并研究了其对红细胞流速度分布的影响。相反，在发散分叉顶点周围没有形成细胞贫化区，结果该区域红细胞与壁面的粘附增强。
