Turbulence‐Intensity Effects on the Aerodynamic Performance of an H‐Type Darrieus Wind Turbine: A URANS Parametric Study

ABSTRACT The effect of inlet turbulence intensity (TI) on the aerodynamic performance of a three‐bladed H‐type Darrieus vertical‐axis wind turbine with NACA 0021 blades was investigated using two‐dimensional (2D) unsteady Reynolds‐averaged Navier–Stokes (URANS) simulations. The realizable model was applied across six TI levels (TI = 1–25%) and five tip speed ratios at a freestream velocity of 9 m/s, producing 30 simulation cases. Validation against the experimental data of Castelli et al. gave a peak‐power coefficient deviation of 3.7% at λ = 2.5. The optimal operating point remained fixed at λ = 2.5 regardless of inlet turbulence, where the power coefficient decreased by 6.0% as TI increased from 5% to 25%. At λ = 1.5, the same increase in turbulence reduced the power coefficient by 17%. A modest nonmonotonic response occurred at , where the power coefficient at TI = 15% was 1.5% higher than the TI = 5% reference value. Instantaneous vorticity contours indicated increasingly diffuse wake structures at higher turbulence intensities. However, these single‐phase contours were insufficient to determine blade‐resolved separation, reattachment, or dynamic‐stall behavior. Within the present 2D framework, the peak‐power condition remained at across the investigated turbulence intensities. Further three‐dimensional analysis is required to determine whether these trends persist for a finite‐span rotor.