Development and Experimental Validation of a Blood Rheology Model based on Extended Micropolar Theory to Increase Accuracy in Flow Simulations and Hemolysis Prediction

• Applicants: Dr.-Ing. Ulrich Kertzscher; Professor Dr. Wolfgang H. Müller
• Subject Area: Mechanics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 549147369

Cardiovascular diseases are the leading cause of death worldwide, accounting for about one-third of global deaths. A common treatment option is the use of blood-guiding devices such as stents, heart valves and ventricular assist devices (VADs). However, these devices have high complication rates, such as thrombus formation, bleeding events or increased damage of red blood cells (hemolysis), due to superphysiological stresses on the blood. In order to reduce the high mortality, the focus of the next decades will be on the development of mathematical and numerical models to predict blood damage based on the flow for new procedures and better devices. For this, a comprehensive knowledge about the physical and chemical properties of blood is required. Consequently, research on hemodynamics is conducted in many fields of study, but there is still a high level of uncertainty due to the complex nature of blood. One major problem in modeling blood is that it is a multi-component mixture with complex rheological properties that cannot be assumed to behave like a Newtonian fluid, because of its substructure of deformable particles. Therefore, there is a high demand in this field for blood models that can simulate these flow phenomena and that can be efficiently integrated into complex flow simulations to predict blood damage. This project is addressing this need by developing an approach that incorporates the homogenized substructure of blood. The chosen approach for this project can be classified as a Generalized Continuum Theory (GCT), incorporating “additional internal degrees of freedom.” For the modeling of blood an extension of Eringen’s microfluids, namely the theory of micropolar fluids, is used. This extended micropolar theory considers a fluid with a substructure of solid particles. In order to include the behavior of RBCs, the theory will now be extended by a microinertia tensor and an associated balance equation to represent the RBC deformation and orientation along with their temporal evolution. Hence, the microinertia tensor is a new field quantity that controls the influence of microstructural effects on micropolar fluid dynamics. Including the microinertia tensor requires deriving a material model that results in a new set of Partial Differential Equations (PDEs) governing the motion of human blood. In order to find material parameters and validate a resulting material model, the flow behavior of human whole blood will be investigated in several clinically-relevant experimental setups to serve as a data basis for the development and validation of the model. The first experimental setups will be designed to measure the material parameters necessary for the blood model in a simple shear flow. The second setup will be designed to simulate the typical loads in blood pumps with short-term stress peaks. In addition, hemolysis is measured and the data provided for the damage model development.

• DFG Programme: Research Grants