Flow and hemocompatibility study of straight-bladed impeller VADs

Ventricular Assist Devices are continuous flow pumps that act as cardiac orthoses. The evaluation of the compatibility of such devices with blood involves, among other aspects, the study of thrombogenicity, hemolysis, and platelet activation. Computational Fluid Dynamics simulation is one of the tools used in this kind of evaluation. Thus, this work used Computational Fluid Dynamics simulations in the analysis of three Ventricular Assist Devices models under development, generating their velocity and pressure contours, their characteristic curves, and the distribution of shear stresses in their walls. A blood model has also been developed in order to estimate the damage inflicted on the blood by the devices. Steady-state simulations were performed, applying the Multiple Reference Frame method. The numerical blood modeling used the Lagrangean approach, with a discrete phase. The estimation of the damage on the blood was based on the relationship between the residence time of the discrete phase and the scalar shear stress. The prototype of one of the models was bench tested to validate the simulations. The simulation results relate the geometry of the models to the characteristics and magnitudes of the recirculation and stagnation regions and to the distribution of shear stresses. The energy performance of each pump and the blood damage index were used as comparison metrics between the devices.