The decrease in apparent relative viscosity that occurs when blood is made to flow through a tube whose diameter is less than about 0.3 mm is a well-known and documented phenomenon in physiology, known as the Fåhræus-Lindqvist effect. However, since the historical work of Fåhræus and Lindqvist (Amer. J. Physiol. 96(3): pp. 562–568, 1931), the underlying physical mechanism has remained enigmatic. A widely accepted qualitative explanation was provided by Haynes (Amer. J. Physiol. 198, pp. 1193–1200, 1960) according to which blood flows in microvessels with a core-annulus structure, where the erythrocytes concentrate within a central core surrounded by a plasma layer. Although sustained by observations, this conjecture lacks a rigorous deduction from the basic principles of continuum dynamics. Moreover, relations aimed to reproduce the blood apparent relative viscosity, extensively used in micro-circulation, are all empirical and not derived from the analysis of the fluid mechanical phenomena involved. In this paper, we apply the recent results illustrated in Guadagni and Farina (Int. J. Nonlinear Mech. 126, p. 103587, 2020), with the purpose of showing that Haynes’ conjecture, slightly corrected to make it more realistic, can be proved and can be used to reach a sound explanation of the Fåhræus-Lindqvist effect based on continuum mechanics. We propose a theoretical model for the blood apparent relative viscosity which is validated by matching not only the original experimental data reported by Fåhræus and Lindqvist (Amer. J. Physiol. 96(3), pp. 562–568, 1931), but also those provided by several subsequent authors.

当血液流过直径小于约 0.3 毫米的管子时，表观相对粘度的降低是生理学中众所周知且有记录的现象，称为 Fåhræus-Lindqvist 效应。然而，自从 Fåhræus 和 Lindqvist (Amer. J. Physiol. 96 (3): pp. 562–568, 1931)的历史工作以来，潜在的物理机制一直是个谜。Haynes (Amer. J. Physiol. 198, pp. 1193–1200, 1960) 据此，血液在具有核心环结构的微血管中流动，其中红细胞集中在被血浆层包围的中央核心内。尽管得到了观察的支持，但这一猜想缺乏从连续体动力学的基本原理中得到的严格推论。此外，旨在重现广泛用于微循环的血液表观相对粘度的关系都是经验性的，而不是从所涉及的流体机械现象的分析中得出的。在本文中，我们应用了 Guadagni 和 Farina（Int. J. Nonlinear Mech. 126，第 103587, 2020)，目的是表明海恩斯的猜想，稍加修正以使其更现实，可以被证明，并可用于基于连续介质力学对 Fåhræus-Lindqvist 效应进行合理解释。我们提出了一种血液表观相对粘度的理论模型，该模型不仅通过匹配 Fåhræus 和 Lindqvist 报告的原始实验数据（Amer. J. Physiol. 96 (3), pp. 562–568, 1931）进行验证，而且还通过匹配由后来的几位作者提供。