In the development of medical fluid device, especially artificial organs and hearts, there have been problems, such as hemolysis (erythrocyte damage) and thrombosis (coagulation of blood) in the device. For hemolysis, the reason and mechanism have not been elucidated yet. There are some factors to occur the hemolysis, for example, molecular viscous shear stress, turbulent shear stress (Reynolds stress), pressure gradient, collision of red blood cells, contact with wall etc. In the recent developments, most popular type of artificial hearts is centrifugal blood pump. But in these pumps, high shear stress, which occurs at the edge of the impeller in the pump and at the lip portion separating the diffuser from the pump casing, is considered as the cause of the hemolysis. As the hemolysis in the flow has physical, biological, and chemical factors, the phenomena is too complicated to analyze.
In this study, to understand the mechanism of hemolysis by shear stress in a complicated flow such as that in a blood pump, the model for hemolysis is constructed using the pipe orifice flow to simplify configurations. In this model, it is considered that there are two methods using effects of the shear stress, and the contact with the wall of orifice including the inertia of the particle caused by differences of density to be considered.