2023
Measured Head-flow HQ curves for a Fontan cavopulmonary assist device (CPAD) in a mock circulatory loop were compared with CFD model predictions. The tests benchmarked the CFD tools for further CPAD design enhancement. Reynolds-Averaged Navier-Stokes (RANS) CFD approaches recommended for development of conventional ventricular assist devices (VAD) were found to have shortcomings when applied to the Fontan CPAD, designed to neutralize off-condition obstruction risks that could contribute to a major adverse event. The no-obstruction condition is achieved with a von Karman type pump, utilizing large clearances and small blade heights, which challenges conventional VAD RANS-based CFD simulations. Accurate head rise and wall shear stress predictions are imperative for pressure boost, power requirement, hemolysis and thrombosis optimizations. Head and power predictions of various RANS turbulence models are compared with pressure test measurements and Large Eddy Simulation (LES) results. The models include standard k-ϵ, RNG k-ϵ, Realizable k-ϵ, SST k-ω, SST with transitional turbulence, and Generalized k-ϵ (GEKO). For the pressure head predictions, the standard k-ϵ model provided the best agreement with experiment, even slightly outperforming the LES. For torque on the rotor, k-ϵ predictions were 30% lower than LES, while the SST and LES values were near identical. The findings support using LES for final Fontan CPAD design simulations. Less preferred is the k-ω model for head and general flow simulation, and SST for power, wall shear stress, hemolysis and thrombogenicity predictions.
CFD Turbulence Model and Experimental Study for a Fontan Cavopulmonary Assist Device