Experimental study on shear stress distributions in a centrifugal blood pump.

Wall shear stress on the pump casing cover was measured using a surface-mounted hot-film sensor. In addition, the shear stress distribution in the pump was qualitatively investigated by means of oil-film visualization. The characteristics of shear stress in the pump are discussed, including the results on the oil-film visualization. The centrifugal blood pump used was a Nikkiso HPM-15 (Nikkiso Co., Ltd, Tokyo, Japan). The hot-film measurement indicated that the shear stress was approximately proportional to the rotating speed, and exceeded 300 Pa when r/R > 0.5 at 3000 rpm. The circumferential average shear stress on the casing cover was of the same order as the characteristic stress sigma obtained from the pump axial torque. These results suggest that the shear stress on the casing cover can be used to evaluate the characteristic shear stress in the pump.