Blood is a complex suspension of red blood cells (RBCs), white blood cells (WBCs), and platelets in an aqueous solution known as plasma, containing dissolved proteins. While many works consider blood as a Newtonian fluid, it exhibits a pronounced non-Newtonian character. This is primarily explained by the ability of RBCs to aggregate/disaggregate, deform, and align to flow.

At low shear rates, blood proteins enhance the formation of a complex network consisting of column-like red cell aggregates, known as rouleaux. In almost stasis, these rouleaux form three-dimensional networks. As shear rates increase, these structures tend to disintegrate, leading to a state where red blood cells flow separately. The dynamic property of blood promoting this non-Newtonian nature necessitates the use of sophisticated rheological models to adequately capture its rheological response. The TEVP (Thixo-elastoviscoplastic) model, initially proposed by Varchanis et al. (2019) and later improved by Giannokostas et al. (2020) and Spyridakis et al. (2024), proves to be an effective model for this purpose.

This presentation will focus on the rheological modeling of blood and its application in hemodynamics, particularly in microcirculation (Giannokostas et al. (2022)).

References:

S Varchanis, G Makrigiorgos, P Moschopoulos, Y Dimakopoulos, J Tsamopoulos. "Modeling the rheology of thixotropic elasto-visco-plastic materials." Journal of Rheology 63 (4), 609-639 (2019).

K Giannokostas, P. Moschopoulos, S. Varchanis, Y. Dimakopoulos, J. Tsamopoulos. "Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Description of the Model and Rheological Predictions." Materials, 13, 4184 (2020). https://doi.org/10.3390/ma13184184

A Spyridakis, P Moschopoulos, S Varchanis, Y Dimakopoulos, J Tsamopoulos. "Thixo-elastoviscoplastic modeling of human blood." Journal of Rheology 68 (1), 1-23 (2024).

K Giannokostas, Y Dimakopoulos, J Tsamopoulos. "Shear stress and intravascular pressure effects on vascular dynamics: Two-phase blood flow in elastic microvessels accounting for passive stresses." Biomechanics and Modeling in Mechanobiology 21 (6), 1659-1684 (2022).