Red blood cells (RBCs)—erythrocytes—suspended in plasma tend to aggregate and form rouleaux. During aggregation the first stage consists in the formation of RBC doublets [S. M. Bertoluzzo, A. Bollini, M. Rasia, and A. Raynal, Blood Cells Mol. Dis. 25, 339 (1999)]. While aggregates are normally dissociated by moderate flow stresses, under some pathological conditions the aggregation becomes irreversible, which leads to high blood viscosity and vessel occlusion. We perform here two-dimensional (2D) simulations to study the doublet dynamics under shear flow in different conditions and its impact on rheology. A few illustrative results obtained here in 3D agree with 2D results. We sum up our results on the dynamics of doublet in a rich phase diagram in the parameter space (flow strength, adhesion energy) showing four different types of doublet configurations and dynamics. We find that membrane tank-treading plays an important role in doublet disaggregation, in agreement with experiments on RBCs. A remarkable feature found here is that when a single cell performs tumbling (by increasing vesicle internal viscosity) the doublet formed due to adhesion (even very weak) remains stable even under a very strong shear rate. It is seen in this regime that an increase of shear rate induces an adaptation of the doublet conformation allowing the aggregate to resist cell-cell detachment. We show that the normalized effective viscosity of doublet suspension increases significantly with the adhesion energy, a fact which should affect blood perfusion in microcirculation.

中文翻译：

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剪切流下的红细胞-红细胞聚集动力学

悬浮在血浆中的红细胞（红细胞）往往会聚集并形成肉串。在聚集过程中，第一步是形成红细胞双峰[SM Bertoluzzo，A。Bollini，M。Rasia，和A. Raynal，Blood Cells Mol。Dis。 25，339（1999）]。尽管聚集体通常会因中等流动应力而解离，但在某些病理条件下，聚集体将变得不可逆，从而导致血液粘度升高和血管闭塞。我们在这里执行二维（2D）模拟，以研究在不同条件下剪切流作用下的双峰动力学及其对流变学的影响。3D此处获得的一些说明性结果与2D结果一致。我们在参数空间（流动强度，粘附能）的丰富相图中总结了关于双峰动力学的结果，该结果显示了四种不同类型的双峰构型和动力学。我们发现，与对RBC进行的实验一致，膜罐踩踏在双峰分解中起着重要作用。此处发现的显着特征是，当单个细胞执行翻滚（通过增加囊泡内部粘度）时，即使在非常高的剪切速率下，由于粘附（甚至非常弱）而形成的双峰仍保持稳定。可以看出，在这种状态下，剪切速率的增加引起了双峰构象的适应，从而使聚集体抵抗细胞-细胞的分离。我们表明，双峰悬浮液的归一化有效粘度随粘附能而显着增加，这一事实应影响微循环中的血液灌注。