The authors studied avoidance of coagulation occurrence using computational
fluid dynamics (CFD) analysis from the fluid dynamical point of view. Conc
erning centrifugal pumps, blood coagulation sometimes occurs at the region
behind the impeller where the flow is generally stagnant. Therefore, we con
ducted a thorough study with the specimen pump with and without washout hol
es, mocking up the Nikkiso HPM-15. As the result, the model with washout ho
les indicated that the fluid rotates rapidly at the vicinity of the shaft a
nd generates washout effects near the stationary rear casing. On the other
hand, the model without washout holes showed that fluid cannot be quickly s
hipped out of the area behind the impeller and rotates mildly around the sh
aft. To clarify the moving relations between the impeller and the fluid, va
lidation studies by comparing the results of CFD analysis and flow visualiz
ation experiments are ongoing; thus far, the studies show that CFD results
are similar to the results from flow visualization experiments.