A FLUID DYNAMIC ANALYSIS OF A ROTARY BLOOD PUMP FOR DESIGN IMPROVEMENT

The proper design of a left ventricular assist device (LVAD) requires an understanding of the pump's fluid dynamic and biocompatible propert ies. A hydraulically efficient system minimizes the power required for pumping. Biocompatibility refers to the ability to pump blood with mi nimal hemolysis and thrombus formation. Typically, shear stresses belo w a threshold level will not damage blood significantly. A fluid dynam ic analysis of a prototype centrifugal pump designed for use as an LVA D was performed to establish flow characteristics. A flow visualizatio n technique using Amberlite particles suspended in a glycerin/water bl ood analogue was used. The system was illuminated with a 1 mm planar b eam strobed helium-neon laser, and the results were recorded photograp hically. An analysis of photographs revealed laminar and turbulent flo ws with vortices within an illuminated plane in both the inlet and out let port areas. From these data, velocity and shear stress profiles we re generated that showed possible areas of improvement. It was conclud ed that the outlet port design could be improved by changing its angle and the continuity of its expansion. The inlet port could also be imp roved by smoothing the transition area between the inlet tube and the pump body to allow for gradual acceleration of the entering fluid.