Experimental Validation of Large Eddy Simulation as a Benchmark for Reynolds-Averaged Navier-Stokes Flow Modeling in a Magnetically Levitated Blood Pump.

PURPOSE: This study investigates the potential of large eddy simulation (LES) as a benchmark for validating Reynolds-averaged Navier-Stokes (RANS) models in the CentriMag centrifugal blood pump. We compare velocity field predictions from LES and RANS against particle image velocimetry (PIV) and quantify previously unreported non-rotatory components in the motion of the magnetically levitated impeller, assessing their impact on flow dynamics.

METHODS

We performed PIV on an optically accessible pump replica and compared phase-averaged velocity fields with computational fluid dynamics (CFD) predictions from LES and three unsteady RANS models. In addition, using custom optical trackers embedded in the PIV setup, we quantified the three-dimensional impeller motion and replicated its main non-rotatory components in the simulations.

RESULTS

The impeller exhibited complex but small deviations from ideal rotation. When incorporated into the CFD model, these had negligible impact on the flow field. LES predictions agreed well with PIV data, with root-mean-square velocity errors of approximately 3%, while the RANS models showed larger local deviations, particularly in the outlet region.

CONCLUSION

LES demonstrated close agreement with PIV and proved to be a reliable reference for validating RANS models in this study. Although the analysis was limited to a single pump, LES warrants further consideration as a potential benchmark method that could reduce reliance on extensive experimental flow validation. Consistent with previous findings, the transition from the volute to the outlet emerged as a particularly sensitive region for RANS modeling and validation. The quantified non-rotatory impeller motion had negligible impact on the flow field, supporting the continued use of idealized rotor motion in CFD modeling of similar magnetically levitated devices.