This study focuses on the fluid dynamics of a blood pump used in extracorporeal membrane oxygenation (ECMO). In ECMO, the patient’s blood is pumped through a circuit composed of a blood pump, membrane lung, tubing, cannulae, and connectors exposing the blood components to highly unsteady flow fields, increasing the risk of blood trauma. The formation of blood clots can be triggered by local flow conditions where areas characterized by high shear and prolonged residence time are particularly problematic. In this work, both Reynolds-averaged Navier–Stokes and large eddy simulation were applied to numerically study the flow details formed in the diagonal ECMO pump DP3 (Xenios AG, Heilbronn, Germany). Three areas of interest were detailed: the inlet backflow caused by a flow cell between the impeller blades, which leads to a vortex roll-up at the pump inlet; the region under the impeller, where a stable rotating flow cell hypothesized to be a contributing factor to potential impeller wobbling; and Taylor–Couette-like structures in the outlet-near areas. All these regions were coupled with highly unsteady stress characteristics. In particular, the results highlight that attention should be focused on separate evaluation of the elongational and the off diagonal components of the shear rate to identify areas of unwanted flow conditions. These should be considered when designing blood pumps as well as understanding their respective influence on the separate blood components.
