Flow visualization study to improve hemocompatibility of a centrifugal blood pump

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.