Shear Evaluation by Quantitative Flow Visualization Near the Casing Surface of a Centrifugal Blood Pump

To clarify the correlation between high-shear flow and hemolysis in blood pumps, detail shear velocity distribution was quantified by an experimental method with a model centrifugal blood pump that has a series data of hemolysis tests and computational fluid dynamic analyses. Particular attention was paid to the shear velocity near the casing surface in the volute where the high shear causes in circumferentially wide region that is considerable to cause high hemolysis. Three pump models were compared concern with the radial gap width between the impeller and casing (the radial volute width) also with the outlet position whereas the impeller geometry was identical. These casing geometries were as follows: model 1-the gap width is standard 3mm and the outlet locates to make a smooth geometrical connection with the volute, model 2-the gap width is small 0.5mm and the outlet locates to make the smooth geometrical connection with the volute, and model 3-the gap width is small 0.5mm and the outlet locates to hardly make the smooth geometrical connection with the volute but be similar radial position with that of model 1. Velocity was quantified with a particle tracking velocimetry that is one of the quantitative flow visualization techniques, and the shear velocity was calculated. Results showed that all large shear velocity existed within the layers of about 0.1mm from the casing surface and that those layers were hardly affected by a vane passage even if the gap width is 0.5mm. They also showed that the maximum shear velocity appeared on the casing surface, and the shear velocities of models 2 and 3 were almost twice as large as that of model 1. This finding is in full corresponding with the results of hemolysis tests which showed that the hemolysis levels of both models 2 and 3 were 1.5 times higher than that of model 1. These results suggest that detailed high-shear evaluation near the casing surface in the volute is one of the most important keys in estimating the hemolysis of a centrifugal blood pump.

[1]  Y Miyazoe,et al.  Computational fluid dynamic analyses to establish design process of centrifugal blood pumps. , 1998, Artificial organs.

[2]  T Tateishi,et al.  A quantitative visualization study of flow in a scaled-up model of a centrifugal blood pump. , 1996, Artificial organs.

[3]  A. Yoganathan,et al.  Investigation of the flow in a centrifugal blood pump. , 1986, ASAIO transactions.

[4]  Harry L. Swinney,et al.  Flow regimes in a circular Couette system with independently rotating cylinders , 1986, Journal of Fluid Mechanics.

[5]  H. Thoma,et al.  Effect of stationary guiding vanes on improvement of the washout behind the rotor in centrifugal blood pumps. , 1992, ASAIO journal.

[6]  Y Nosé,et al.  A compact centrifugal pump for cardiopulmonary bypass. , 2008, Artificial organs.

[7]  S. Hashimoto,et al.  Effect of shear rate on clot growth at foreign surfaces. , 1985, Artificial Organs.

[8]  Y Miyazoe,et al.  Development of design methods of a centrifugal blood pump with in vitro tests, flow visualization, and computational fluid dynamics: results in hemolysis tests. , 1998, Artificial organs.

[9]  Y Miyazoe,et al.  Flow visualization as a complementary tool to hemolysis testing in the development of centrifugal blood pumps. , 1998, Artificial organs.

[10]  B Asztalos,et al.  Quantitative visualization of flow through a centrifugal blood pump: effect of washout holes. , 1997, Artificial organs.

[11]  Y Nosé,et al.  A fluid dynamic analysis of a rotary blood pump for design improvement. , 2008, Artificial organs.

[12]  Y Miyazoe,et al.  Flow visualization study to improve hemocompatibility of a centrifugal blood pump. , 1999, Artificial organs.

[13]  Y Miyazoe,et al.  Computational fluid dynamics analysis to establish the design process of a centrifugal blood pump: second report. , 1999, Artificial organs.

[14]  T Noda,et al.  Development of an atraumatic small centrifugal pump for second-generation cardiopulmonary bypass. , 2008, Artificial organs.

[15]  I. Sakuma,et al.  Flow visualization evaluation of secondary flow in a centrifugal blood pump. , 1993, ASAIO journal.

[16]  Y Miyazoe,et al.  Development of design methods for a centrifugal blood pump with a fluid dynamic approach: results in hemolysis tests. , 1999, Artificial organs.