In vitro LDA and flow visualization analysis of the spiral vortex pump: effect of inlet valve orientation

Abstract

The spiral vortex pump (SV), an innovative, penumatically driven ventricular assist device, was tested using the flow visualization technique and laser Doppler anemometry to study the effect of inlet valve orientation under steady and pulsatile flow conditions in a purposely constructed flow circuit aimed at obtaining flow field data. Qualitative information was obtained using the flow visualization technique. The slit-lighting technique and fluorescent bees provided a clear flow field view at the desired location, and a 200 frames/s high-speed video camera was used, capturing the vortex nature of the flow field. Mean velocity and fluctuating velocity profile were obtained using a Kanomax single-channel FLV system. Three diametrically transverse locations and three vertical locations were selected for measurements. The particle-tracking method was also incorporated to obtain velocity vectors. Based on the experimental data, the following general conclusions can be drawn: (1) The SV pump created a vortex flow field under steady and pulsatile flow conditions. (2) The inlet valve orientation sharply influenced the flow inside the SV pump. (3) A relatively strong circulatory flow field was observed when the major orifice was oriented toward the HD junction under steady flow. (4) A relatively weak circulatory flow field was observed when the major orifice was oriented toward the center under steady flow. (5) The directional flow field was more accentuated under pulsatile flow conditions. (6) A relatively stable flow field was observed when the major orifice was oriented upward (pump outlet direction). (7) Directional flow toward the diaphragm was observed when the major orifice was oriented downward. (8) A strong circulatory flow with possible colliding flow toward the peripheral area was observed when the major orifice was oriented outward. (9) A relatively weak circulatory flow was observed when the major orifice was oriented inward. (10) The strength of the circulatory flow during the peak flow phase under pulsatile conditions was not affected by the orientation of the inlet valve.