| Although there are many studies that focus on the fluid mechanics within ventricular assist devices (VADs), the impact of VAD anastomoses on the aortic flow has been largely ignored. Hence, we study the blood flow within the end-to-side anastomoses of VADs to adult and pediatric aortas. The great vessels originating from the aortic arch are included to study flow splitting. A second-order accurate time-dependent flow solver based finite volume method is used to simulate the flow. Monotone integrated large eddy simulation is used to resolve large scales of the resulting turbulent flow based on grid cut-off and to model the sub-grid scale (SGS) motions using non-linear built-in (implicit) SGS turbulence models. Hemolysis is modeled using an advection-reaction transport equation. The flow solver is validated against analytical and experimental results. The effect of blood viscoelasticity is examined experimentally using particle image velocimentry. Our results suggest that the VAD anastomosis significantly alters the flow in the aorta. A proximal anastomotic configuration diverts an impingement jet into the brachiocephalic artery and may increase the perioperative right-sided stroke rate, whereas a distal anastomotic configuration leads to a large stagnant region near the aortic valve and possible thrombosis. Turbulence occurs for both configurations during the complete VAD support. The continuous support significantly reduces the blood damage in the aorta when compared to the pulsatile support, although it could lead to end-organ failure as a result of the reduced pulsatility. This work may help to identify the risk of graft failure for patients with VAD assistance. |
