ELIMINATION OF REVERSAL FLOW IN BACK CLEARANCE GAPS OF A MINIATURE PEDIATRIC CENTRIFUGALBLOOD PUMP BY CFD

Abstract

The configuration of a centrifugal pump has been widely used as a ventricular assist device (VAD) for adults and recently for infants and small children with failing ventricles. For such a centrifugal pump, the back clearance gap together with the central core and outer annular clearance gap jointly form a washout flow path. However, within the washout path, the flow demonstrates a complex 3-dimensional structure, whcih potentially causes cellular trauma and/or thrombosis and also affects hydrodynamic performance. The objective of this study was to eliminate the reversal flow in the back clearance gaps of a miniature pediatric centrifugal blood pump by CFD analyses and design optimization. A commercial CFD code, Star-CD, was utilized to simulate the 3-D blood flow within a miniature centrifugal pump. An implicit method based on multiple reference frames was used for the coupling between the rotational and stationary elements. A power law function was integrated into the code to evaluate hemolysis with the shear history being recorded by the Lagrangian particle tracking method. By CFD analyses and optimization design, it was found that secondary blades, located along the lower and side surfaces of the rotor, can generate antegrade blood flow in the clearance gaps. Through optimizing the secondary blades number and their geometry by CFD, we were able to achieve net antegrade flow with minimal zones of retrograde flow.