PREDICTION OF HEMOLYSIS IN TURBULENT SHEAR ORIFICE FLOW

This study proposes a method of predicting hemolysis induced by turbul ent shear stress (Reynolds stress) in a simplified orifice pipe flow. In developing centrifugal blood pumps, there has been a serious proble m with hemolysis at the impeller or casing edge; because of flow separ ation and turbulence in these regions. In the present study, hemolysis caused by turbulent shear stress must occur at high shear stress leve ls in regions near the edge of an orifice pipe flow. We have computed turbulent shear flow using the low-Reynolds number k - epsilon model. We found that the computed turbulent shear stress near the edge was se veral hundreds times that of the laminar shear stress (molecular shear stress). The peak turbulent shear stress is much greater than that ob tained in conventional hemolysis testing using a viscometer apparatus. Thus, these high turbulent shear stresses should not be ignored in es timating hemolysis in this blood flow. Using an integrated power by sh ear force, it is optimimal to determine the threshold of the turbulent shear stress by comparing computed stress levels with those of hemoly sis experiments of pipe orifice blood flow.