Particle image velocimetry measurements of blood velocity in a continuous flow ventricular assist device

The third prototype of a continuous flow ventricular assist device (CFVAD3) is being developed and tested for implantation in humans. The blood in the pump flows through a fully shrouded four-bladed impeller (supported by mag netic bearings) and through small clearance regions on either side of the i mpeller. Measurements of velocities using particle image velocimetry of a f luid with the same viscosity as blood have been made in one of these cleara nce regions. Particle image velocimetry is a technique that measures the in stantaneous velocity field within an illuminated plane of the fluid field b y scattering light from particles added to the fluid. These measurements ha ve been used to improve understanding of the fluid dynamics within these cr itical regions, which are possible locations of both high shear and stagnat ion, both of which are to be avoided in a blood pump. Computational models of the pump exist and these models are currently being used to aid in the d esign of future prototypes. Among other things, these models are used to pr edict the potential for hemolysis and thrombosis. Measurements of steady fl ow at two operating speeds and flow rates are presented. The measurements a re compared with the computed solutions to validate and refine, where neces sary, the existing computational models.