Impact of Tip Clearance on the Flow Features and Blood Trauma of a Centrifugal Blood Pump Under Multiple Operating Conditions
TL;DR
The findings indicate that the effects of tip clearance on flow dynamics, energy dissipation, and hemolysis are strongly condition dependent, providing guidance for clearance design in centrifugal blood pumps across clinically relevant operating ranges.
Abstract
Blade tip clearance plays an important role in the hydraulic performance and hemocompatibility of centrifugal blood pumps, yet its effects across clinically relevant operating conditions, particularly off-design conditions, remain insufficiently understood. In this study, computational fluid dynamics (CFD) simulations were combined with vortex dynamics and energy dissipation analyses, were used to investigate four tip clearance sizes (0.2–0.8 mm) in a fully magnetically levitated centrifugal blood pump with a semi-open impeller. The pump was evaluated under a low-flow mode, a nominal design mode, and a high-flow mode. Increasing tip clearance intensified the tip leakage vortex and secondary recirculation, leading to reductions in pressure head and hydraulic efficiency. It also redistributed energy dissipation, with direct viscous dissipation decreasing, turbulent dissipation increasing, and high-dissipation regions extending from the tip clearance region into the main flow passage. The hemolysis index exhibited marked operating-condition dependence, showing a nonmonotonic response under the nominal adult design and high-flow modes but a monotonic decrease under the low-flow mode. These findings indicate that the effects of tip clearance on flow dynamics, energy dissipation, and hemolysis are strongly condition dependent, providing guidance for clearance design in centrifugal blood pumps across clinically relevant operating ranges.