Hiroyuki Onuma

Magnetically suspended centrifugal blood pump with a self bearing motor.

A magnetically suspended centrifugal blood pump with a self bearing motor has been developed for long-term ventricular assistance. A rotor of the self bearing motor is actively suspended and rotated by an electromagnetic field without mechanical bearings. Radial position of the rotor is controlled actively, and axial position of the rotor is passively stable within the thin rotor structure. An open impeller and a semi-opened impeller were examined to determine the best impeller structure. The outer diameter and height of the impeller are 63 and 34 mm, respectively. Both the impellers indicated similar pump performance. Single volute and double volute structures were also tested to confirm the performance of the double volute. Power consumption for levitation and radial displacement of the impeller with a rotational speed of 1,500 rpm were 0.7 W and 0.04 mm in the double volute, while those in the single volute were 1.3 W and 0.07 mm, respectively. The stator of the self bearing motor was redesigned to avoid magnetic saturation and improve motor performance. Maximum flow rate and pressure head were 9 L/min and 250 mm Hg, respectively. The developed magnetically suspended centrifugal blood pump is a candidate for an implantable left ventricular assist device.

Comparison of CFD Simulation to the Experiments for Forward Step Flows

Three dimensional DNS simulation on the fluid flow over a forward step configuration are compared with the experiments reported by Shakouchi, Ando, and Ito. This is a part of authors’ attempts to evaluate the validity of three dimensional unsteady flow simulation by comparison to experiments. Summary of the comparison is as follows: (1) vortex shedding in the flow separation over the top of the step near the corner is observed, (2) frequency of vortex shedding and distance between two consecutive vortices do not agree with the experiment, (3) however, while steady periodic shedding of vortices from the top corner of the step is reported for the experimental results, the computational results show unsteady behavior of the flow over the top corner, which results in unsteady shedding of vortices. This unsteadiness in the computational simulation is due to unsteady motion of fluid upstream from the step where adverse pressure increase occurs.© 2003 ASME