A fully physiologically-informed time- and rate-dependent hemorheological constitutive model

From a mechanical perspective, blood is a complex fluid with a rate- and time-dependent response to an applied deformation. At small deformation rates, cell aggregations owing to the bridging of fibrinogen proteins result in the formation of rouleaux structures manifesting in a large increase in the overall viscosity of the blood viscosity and the emergence of measurable yield stress. At elevated deformation rates, these internal aggregated mesostructures are broken down in a dynamical fashion, giving rise to a thermokinematic memory and thixotropic behavior of the blood. These rich and complex rheological features of blood are primarily governed by the interactions between different cells as well as the fraction of red blood cells (RBCs). Here, using a series of detailed computational tools and benchmarking experimental measurements, we present a constitutive model that accurately describes the rate- and time-dependent rheology of blood based on two physiological metrics of the blood: the hematocrit and fibrinogen concentration. We show that the model is capable of accurately predicting blood flow, not only under simple steady flows but also under different flow protocols relevant to a real circulatory system.