CFD Verifies The Effect Of Impeller Design On Blood Pump Flow Patterns And Shear Distribution

Computational Fluid Dynamics (CFD) as a tool for numerical simulation can predict various complex flow and mass transfer phenomena, and can provide visualized results; thus it has been widely applied in various scientific fields. In the study of artificial heart pumps, CFD has become a viable technology assisting blood pump design and evaluating its performance.From Navier-Stokes equations, the discretization theory of CFD and several numerical methods, as well as the procedure of simulation and various turbulence models are introduced. CFD is applied to predict the flow in the blood pump developed by Inst. Biomed. Eng. Univ. of Jiangsu and American Biopump with straight vanes.The results show :(1 )The absolute velocity and pressure in the impellers increase along the flow path and reach the maximum at the exit of flow path, and the pressure has a radial uniform distribution. All these agree with the theoretical analysis.(2) The relative velocity field in the blood pump based on stream-lined design appears to be a laminar flow, the stream lines and stream surfaces are coincident with the vanes anywhere, without flow separation, stagnation and re-circulation. Under the same boundary conditions, the stream lines of the main flow in Bio-pump are logarithmic spirals same as these in stream-lined design. The flow separation occurs between the main flow and the straight vanes and shrouds, and flow stagnation, re-circulation emerge in some areas. It is concluded that in same boundary conditions blood pumps based on stream-lined design have better blood compatibility and anti-thrombogenicity.(3) The maximum shear on the stream-lined impeller walls is 186Pa, while the maximum shear of the Bio-pump with straight vanes is 280Pa. In the impeller wall of the stream-lined blood pump, there is no nodes by which the shear beyond the critical value(150Pa) leading to hemolysis according to Niimi H et al, while the nodes by which the shear beyond the critical value are as high as 74 in the walls of straight vanes and shrouds. This proves once again that blood pumps based on stream-lined design has lower hemolysis than pumps with straight vanes.