Numerical Study of Particle Margination in a Square Channel Flow with Red Blood Cells
Numerical Study of Particle Margination in a Square Channel Flow with Red Blood Cells
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DOI：
10.3390/fluids7030096
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发表时间：
2022-03
期刊：
影响因子：
1.9
通讯作者：
Dongig Oh;Satoshi Ii;S. Takagi
中科院分区：
文献类型：
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作者：
Dongig Oh;Satoshi Ii;S. Takagi
红细胞在小血管中轴附近流动，称为轴向聚集。这导致了一个称为无细胞层的区域，该区域在壁附近不包含红细胞。然后，小颗粒如血小板出来到无细胞层。这种现象称为血小板边缘化。在这项研究中，有关这一现象，直接数值模拟进行了使用浸没边界法。研究了剪切速率、通道尺寸和红细胞压积对压力驱动方形截面直管内流动的影响。模拟结果表明，边集率，这是在流动方向上的移动距离的比率，在壁方向上的边集距离，是独立的剪切速率。通过引入无量纲参数，其中包括颗粒运动的剪切速率和有效面积，发现通道尺寸对血小板附聚的影响被很好地缩放。同时发现边集率与试管红细胞压积呈非线性关系。这是由于红细胞的体积排阻效应，其根据红细胞比容促进或阻碍颗粒的运动。此外，还得到了颗粒在拐角处的稳定位置与无胞层宽度的关系，并发现在模拟过程中，由壁面剪切率归一化的速度脉动在截面上趋于一条曲线。这表明作用在颗粒上的侧向力随剪切速率线性增加。
Red blood cells flow near the axis in a small vessel, known as axial accumulation. This causes a region called the cell-free layer, which does not contain red blood cells near the wall. Then, small particles such as platelets come out to the cell-free layer. This phenomenon is called platelet margination. In this study, related to this phenomenon, direct numerical simulations were conducted using the immersed boundary method. The effects of the shear rate, channel size, and hematocrit value were investigated on the pressure-driven flow in a straight tube with a square cross-section. The simulation results indicated that the margination rate, which is the ratio of the distance traveled in the flow direction to the margination distance in the wall direction, is independent of the shear rate. The effect of the channel size on platelet margination was found to be well scaled by introducing a dimensionless parameter, which included the shear rate and effective area of the particle movement. It was also found that the margination rate varied nonlinearly with the tube hematocrit. This was due to the volume exclusion effect of red blood cells, which facilitated or hindered the motion of particles depending on the hematocrit. The relationship between the stable position of the particles near the corner and the width of the cell-free layer was also found. Furthermore, velocity fluctuations normalized by wall shear rate in a cross-section collapsed to one curve in the presented simulations. This indicates that the lateral force acting on the particles increases linearly with the shear rate.