Visualization of relative flow patterns in centrifugal blood pump

This paper presents computational and flow visualization results on a centr ifugal blood pump, 4 impeller designs were tested at a rotational speed of 2000 rpm using blood analog as working fluid. All impellers have seven blad es but of different geometry (Impellers A3. A4, B2 and R7). Flow visualizat ion within the impeller passages was conducted using an image de-rotation s ystem. A pair of large scale vortices was found within the blades of impell er R7 while a single vortex was found in most of the passages of backward f acing impellers (Impellers A3, A4 and B2). To establish the effects of blad e geometry on blood cells, CFD was used to simulate the blade to blade flow to provide an estimate of the maximum shear stress. The results showed tha t though most of the stresses within the blade passages are below a thresho ld level of 150 N/m(2) for extensive erythrocyte damage to occur, there are some regions near to the leading edge of the pressure side where the shear stresses are above threshold level.