Comparison of Blade Resolved and Actuator Disk Simulations of a Ducted Wind Turbine

Abstract. 3-D blade-resolved and 2-D actuator-disk simulations of a ducted wind turbine (DWT) were performed to investigate the fidelity of actuator disc predictions and the impact of 3-D effects on performance. Both simulations used Reynolds-averaged Navier-Stokes (RANS) equations with a k-ϵ turbulence model. The DWT had a five-bladed rotor with a GOE417a airfoil, and the duct utilized an E423 airfoil. The Reynolds number based on the diameter of the rotor was 1.24 × 10^6. The design tip speed ratio was 2.9. The performance of the DWT from the blade-resolved simulation was 26 % lower than the actuator disk simulation, with a significantly larger separation region inside the duct. These observations suggest that, while 2-D actuator disk simulations have a lower computational cost, predictions of the coefficient of power and flow separation may not be accurate. A possible reason is that the actuator disc model did not include swirl, which near the hub was observed to reach nearly 80 % of the free stream velocity. Another possible reason is blade intermittency effects. The separation region on the duct increased as the blade passed and then reduced, but it was always larger than that in the actuator disk simulations.