Numerical and in vitro investigations of pressure rise in a new hydrodynamic blood bearing.

The reliability and simplicity of rotor bearing are vital to the success of long-term implantation of rotary blood pumps. This article describes both numerical and in vitro studies of the pressure rise in a 5-cm-diameter spiral groove bearing. Results show that the simplified analytical model overpredicts the pressure rise across the bearing while the results from a more comprehensive three-dimensional computational fluid dynamics (CFD) model agree well with the measurements. The discrepancy between the analytical model and the measurements is attributed to the exclusion of the fluid inertia effects in the analytical model. In addition, the assumption of linear pressure variations at the entrance of the groove and the ridge may have oversimplified the analysis. CFD results show that the pressure variation at the entrance of the groove and ridge is nonlinear. A correction factor taking into consideration the fluid inertia effect has been incorporated, and the modified analytical results agreed well with the measurement as well as that of the more comprehensive CFD model. The pressure generated is sufficient to lift the rotor, and this design provides the designer an alternative design for passive bearing.