Many of the intriguing properties of blood originate from its cellular nature. Bulk effects, such as viscosity, depend on the local shear rates and on the size of the vessels. While empirical descriptions of bulk rheology are available for decades, their validity is limited to the experimental conditions they were observed under. These are typically artificial scenarios (e.g., perfectly straight glass tube or in pure shear with no gradients). Such conditions make experimental measurements simpler, however, they do not exist in real systems (i.e., in a real human circulatory system). Therefore, as we strive to increase our understanding on the cardiovascular system and improve the accuracy of our computational predictions, we need to incorporate a more comprehensive description of the cellular nature of blood. This, however, presents several computational challenges that can only be addressed by high performance computing. In this chapter we describe HemoCell , an open-source high performance cellular blood flow simulation, which implements validated mechanical models for red blood cells and is capable of reproducing the emergent transport characteristics of such a complex cellular system. We discuss the accuracy, the range of validity, and demonstrate applications on a series of human diseases.

翻译：血液的诸多特性源于其细胞本质。黏度等宏观效应取决于局部剪切速率及血管尺寸。尽管对宏观流变学的经验描述已存在数十年，但其有效性仅限于观察实验条件——这些条件通常是人为场景（例如完美笔直的玻璃管或无梯度的纯剪切流）。此类条件简化了实验测量，但在真实系统（如人体循环系统）中并不存在。因此，为了加深对心血管系统的理解并提升计算预测的准确性，我们需要纳入对血液细胞本质更全面的描述。然而，这带来了诸多计算挑战，唯有通过高性能计算才能应对。本章介绍HemoCell——一个开源的高性能细胞血流模拟框架。该框架实现了经过验证的红细胞力学模型，能够复现此类复杂细胞系统涌现的输运特性。我们讨论了其准确性、适用范围，并展示了在系列人类疾病中的应用。