Measurements by laser Doppler velocimetry in the casing/impeller clearance gap of a biocentrifugal ventricular assist device model.

The velocity distributions in the clearance gap of the Kyoto-NTN biocentrifugal ventricular assist device model were measured by laser Doppler velocimetry (LDV) at three inlet flow conditions, namely operating, fully opened, and fully closed conditions. The results obtained have a similar trend as in the earlier measurements using air as medium and the hot-wire probe, a washout mechanism that is a segment of fluids in the gap situated from theta = 60 degrees to 220 degrees, has a larger radial velocity component flowing toward the eye of the pump, as compared to other regions in the gap where the tangential velocity component is dominant. It is essential to have a good washout for the leakage flow through the clearance gap between the stationary casing and the impeller of the pump so that the blood will not keep on circulating in the gap but is washed out to the eye in order to reduce the chances of being destroyed.

Experimental study of a complete anastomosis model for the coronary artery bypass.

Local hemodynamics of complete bypass model under steady flow condition was investigated using the instantaneous velocity fields acquired by Particle Image Velocimetry (PIV). At proximal anastomosis a low velocity region was found near the heel along the graft inner wall and a stagnation point was found near the toe. The velocity profile was relatively smooth except slightly skew toward the graft outer wall.