A correlation study was conducted among quantitative flow visualization ana
lysis, computational fluid dynamic analysis, and hemolysis tests regarding
the flow in a centrifugal blood pump to prevent hemolysis. Particular atten
tion was paid to the effect of the impeller/casing gap widths on the flow i
n the volute and in the outlet. Flow vector maps were obtained for 250% sca
led-up models with various geometries, using an argon ion laser light sheet
, a high speed video camera, and particle tracking velocimetry, In terms of
the results, in the small radial gap model, high shear occurred near the i
nside wall of the outlet and stagnation near the outside wall of the outlet
whereas the standard model maintained smooth flow and low shear. The small
radial gap model showed a lower head and greater hemolysis than the standa
rd model. This head decrease could be partly restored by relocating the out
let position; however, the hemolysis level hardly decreased. From these res
ults, it was found that the small radial gap itself is important. It was al
so confirmed by detailed flow visualization and simple laminar shear analys
is near the wall that the small radial gap caused a wider high shear layer
(110-120 mu m) than the standard model (-80 mu m). In the small radial gap
model, the high shear layer in the outlet (-50 mu m) is much narrower than
that in the volute. Flow visualization together with the aid of computation
al fluid dynamic analysis would be useful to eliminate the causes of hemoly
sis.