Characterizing blood hysteresis via tensorial thixo-elasto-viscoplastic modeling

Abstract

A characteristic feature of human blood rheology is a distinctive stress hysteresis during shear ramp up in the shear rate from zero, followed by a ramp back to zero. This is a result of the fact that human blood has a longer characteristic time of shear-induced rouleaux breakdown compared to the shear aggregation of the rouleaux. We demonstrate this telltale phenomenon of human blood rheology during the triangle ramp, time-dependent change in the shear rate. The unique hysteresis data are then used along with steady state data to fit parameters of a recently published thixo-elasto-viscoplastic rheological model, the tensorial enhanced structural stress thixotropic-viscoelastic (t-ESSTV) model. These best-fit parameter values from the hysteresis ramps are then used to predict step-up/down in shear, small amplitude oscillatory shear, uni-directional large amplitude oscillatory shear, and large amplitude oscillatory shear flow. Additionally, correlations between the calculated fitting parameters and physiological data are analyzed to inform the interpretation of model behavior in physical terms. The fit adherence to the triangle ramp and rheological hysteresis data are then evaluated alongside recently developed techniques to assess thixotropy via hysteresis loop area, indicating the efficacy of the t-ESSTV model in potentially predicting blood's complex characteristics in useful ways for future use in modeling blood flows under a variety of mechanical and biological conditions and predicting pathologies.