EVALUATION OF BLOOD COMPATIBILITY OF A CENTRIFUGAL BLOOD PUMP BASED ON THE TRANSIENT FLOW VELOCITY MEASUREMENT FROM THE ROTATING FRAME.

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Flow visualization method has been developed which enables the direct observation and measurement of the relative velocity distribution in the impeller of a centrifugal pump used for cardiac assist. The image rotator containing a beam splitter and a right-angle prism was applied to the double-scale model of a centrifugal pump. The transient flow velocity distribution was measured by the particle image velocimetry (PIV) technique.The results also demonstrated that the passages of the impeller were filled with vortices of various scales, which seemed to contribute to prevention of thrombus formation on the blood-contacting surface of the impeller. The emission from the impeller toward the outlet port was limited to the period when the passage overlapped the area of the outlet port. This unsteadiness was found to be adverse in terms of the pump's hydrodynamic efficiency and the radial thrust. It was moderated by the use of the volute casing. It should be noted, however, that the axial variation of the flow field was enlarged.