Numerical simulation of platelet adhesion, activation and aggregation Application to Taylor-Couette systems

Background: Heart attack and stroke are among the leading causes of death in industrial nations but the number of candidates needing a transplant exceeds the number of transplants performed. Due to this chronic shortage, blood pumps are needed to deliver appropriate hydraulic performance while maintaining physiological flow conditions. Because all known artificial materials are considered to be thrombogenic to some extent it is necessary to investigate the interaction of flow and material in complex geometries to optimize modern blood pumps and other artificial organs. As human blood is a precious fluid, designers of rotational blood pumps desire reliable predictive thrombosis models to optimize the physiological compatibility of their devices. In this thesis, the initial development stage of a model for platelet adhesion, activation and aggregation is described. Model equations and methods for their numerical solution are presented. The Taylor-Couette system, as a well investigated rotational device, is simulated as a test case to estimate model parameters and to explore the predictive accuracy of the model. Results: Adhesion rates for polystyrene surfaces were obtained by fitting numerical simulations to experimental results for laminar flow. These parameters were used to simulate the effects on the platelets in Taylor vortex flow based on a pre-computed velocity field. Conclusions: Without proper care, fitting can result in unphysiological model parameters. Numerical optimization methods can help finding better parameters, but cannot yet entirely replace parameter guessing. Platelet migration and other shear-dependent effects will have to be included in the model to reproduce the results in case of Taylor vortex flow.