纳微尺度颗粒在管状血流中弥散的统一分析
A unified analysis of nano-to-microscale particle dispersion in tubular blood flow
摘要：
当颗粒从纳米级变化到微米级尺寸时，与红细胞（RBC）相比，固体颗粒在血流中的运输表现出运输机制的质的差异。几个小组已经研究了微尺度颗粒边缘化的影响。此外，血液中纳米颗粒（NPs）的运输在过去也受到了相当大的关注。这项研究试图通过定量地显示传输机制如何随颗粒尺寸从纳米到微米尺度而变化来弥合这一差距。使用三维（3D）的多尺度方法，在微尺度的管状流的颗粒的分散进行了研究，为各种血细胞比容，血管直径和颗粒尺寸。由于严重的布朗运动，纳米颗粒在整个管半径上表现出不均匀的、平滑分散的分布。通过增加红细胞压积和限制，可以适度增强NP的近壁浓度。此外，存在临界颗粒尺寸（$\sim$ 1 $μ$ m），其导致颗粒过度保留在壁附近的无细胞区域中，即，边缘化在该阈值以上，边集倾向随着颗粒尺寸而增加。RBC增强的剪切诱导扩散率（RESID）超过布朗扩散率（BD）的优势导致RBC负载区域中的径向扩散速率比无细胞层中的径向扩散速率高10倍，这与微尺度颗粒的高边缘化倾向相关。这项工作捕获的颗粒尺寸依赖的过渡从布朗运动占主导地位的分散边缘使用统一的三维多尺度计算方法，并突出了径向分布的RESID和边缘的粒子在受限的血流之间的联系。
英文摘要：
Transport of solid particles in blood flow exhibits qualitative differences in the transport mechanism when the particle varies from nanoscale to microscale size comparable to the red blood cell (RBC). The effect of microscale particle margination has been investigated by several groups. Also, the transport of nanoscale particles (NPs) in blood has received considerable attention in the past. This study attempts to bridge the gap by quantitatively showing how the transport mechanism varies with particle size from nano- to microscale. Using a three-dimensional (3D) multiscale method, the dispersion of particles in microscale tubular flows is investigated for various hematocrits, vessel diameters and particle sizes. NPs exhibit a nonuniform, smoothly-dispersed distribution across the tube radius due to severe Brownian motion. The near-wall concentration of NPs can be moderately enhanced by increasing hematocrit and confinement. Moreover, there exists a critical particle size ($\sim$1 $μ$m) that leads to excessive retention of particles in the cell-free region near the wall, i.e., margination. Above this threshold, the margination propensity increases with the particle size. The dominance of RBC-enhanced shear-induced diffusivity (RESID) over Brownian diffusivity (BD) results in 10 times higher radial diffusion rates in the RBC-laden region compared to that in the cell-free layer, correlated with the high margination propensity of microscale particles. This work captures the particle size-dependent transition from Brownian-motion dominant dispersion to margination using a unified 3D multiscale computational approach, and highlights the linkage between the radial distribution of RESID and the margination of particles in confined blood flows.
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