Study of leakage flow in an axial LVAD with varying tip clearance

Background: Design optimization of Left Ventricular Assist Devices (LVADs) has been of global interest in the recent years due to the alarming rise in the heart failure cases. A topic less discussed in the literature, leakage flow, is taken up for study. Leakage flow is critical for blood damage as it increases the exposure time of RBCs on high shear stress areas. Design a better LVAD with leakage flow patterns and hence leading to a smaller machine leading to better implantability. This study uses CFD in comparing tip leakage flow in two pump impeller blade designs, one with an isochrous blade thickness of 0.5mm to another with blade thickness varying along its length, for different tip clearance gap configurations. It is found that, for a given geometry, the leakage flow pattern reduces as the tip clearance reduces, while the wall shear stress value increases. The optimum value of clearance gap for design with a constant blade thickness and one with a varying blade thickness are found out by limiting the maximum WSS. It has been proved that blade thickness modification is a suitable method to reduce blood damage and improve pump efficiency