Combining Rheology and Simulations to Model Bulk Blood Flow

Understanding blood flow is an active area of research due to its potential to improve drug delivery, importance in design of medical devices, and role in health complications. However, modeling blood flow is difficult because of both the complex flow geometries and the unique rheology of blood. The rheology of blood is characterized by a shear thinning behavior with a nonzero yield stress, viscoelasticity, and thixotropy – a time dependent change in the viscosity. These features arise as a result of the coin stack microstructures called rouleaux that red blood cells (RBCs) form under stasis and low shear. In this work, we present new data on human blood bulk rheology and offer a thixotropic rheological model for transient blood flow. The model includes a structural term and a viscoelastic term relating to the RBC deformability. Additionally, flow inhomogeneities that occur within blood are discussed and a representation of these effects is proposed. Finally, the rheological model is incorporated into flow simulations of blood through circulatory system portions, and from a comparison with a Newtonian model, the significance of the rheology in blood flow simulations is identified.