Poletti Gianluca, Bardón Ricardo Gómez, Dubini Gabriele, Pennati Giancarlo
LaBS - Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy.
Ann Biomed Eng. 2025 Feb;53(2):507-519. doi: 10.1007/s10439-024-03644-4. Epub 2024 Nov 12.
Blood is commonly treated as single-phase homogeneous fluid in numerical simulations of blood flow within fiber bundles of blood oxygenators. However, microfluidics tests revealed the presence of hematocrit heterogeneity in blood flowing across such geometries. Given the significant role of red blood cells (RBCs) in the oxygenation process, this study aims to propose a multiphase blood model able to correctly describe the experimental evidence and computationally investigate hematocrit heterogeneities inside fiber bundles.
The experimental results of microfluidics tests performed in a previous study were processed and based on quantitative data of image intensity, a two-phase blood model following the Eulerian-Eulerian approach was calibrated and evaluated in its predictive ability against the experimental data. The two-phase model was then used to study the RBCs distribution inside different fiber bundles at average hematocrit values of 25% and 35%, representative of hemodilution in extracorporeal blood circulation.
The numerical model proved to be able to describe and predict the experimental phase separation between plasma and RBCs within the microchannel geometry at different test conditions. Moreover, blood flow simulation in commercial fiber bundles revealed the presence of specific patterns in hematocrit distribution and their dependence on variations in bundle microstructure.
The two-phase blood model proposed in this study provides a tool for advanced evaluation of local fluid dynamics and identification of optimal bundle microstructure allowing further gas transfer simulations to account for a reliable heterogeneous distribution of RBCs around the oxygenating fibers.
在对血液氧合器纤维束内的血流进行数值模拟时，血液通常被视为单相均匀流体。然而，微流体测试显示，在流经此类几何结构的血液中存在血细胞比容异质性。鉴于红细胞（RBC）在氧合过程中的重要作用，本研究旨在提出一种多相血液模型，该模型能够正确描述实验证据，并通过计算研究纤维束内的血细胞比容异质性。
对先前研究中进行的微流体测试的实验结果进行处理，并基于图像强度的定量数据，校准了一种遵循欧拉-欧拉方法的两相血液模型，并评估了其对实验数据的预测能力。然后使用该两相模型研究平均血细胞比容值分别为25%和35%的不同纤维束内红细胞的分布情况，这两个值代表体外血液循环中的血液稀释情况。
数值模型被证明能够描述和预测在不同测试条件下微通道几何结构内血浆和红细胞之间的实验相分离。此外，对商用纤维束内血流的模拟揭示了血细胞比容分布中的特定模式及其对束微观结构变化的依赖性。
本研究提出的两相血液模型为深入评估局部流体动力学和确定最佳束微观结构提供了一种工具，从而能够在进一步的气体传输模拟中考虑红细胞在氧合纤维周围可靠的非均匀分布。
