Balancing Actuation Penalties and Wake Recovery: The Efficacy of the Helix in Turbulent Inflows

Abstract The Helix approach mitigates wake losses by employing periodic dynamic individual pitch control to force the wake into a helical structure, thereby accelerating wake recovery through increased ambient mixing. While proven in idealized flows, its operational viability under realistic atmospheric turbulence remains under-characterized. This study isolates the impact of ambient Turbulence Intensity (TI) on Helix efficacy using high-fidelity Large Eddy Simulations (LES) of the IEA-22MW reference turbine. We evaluate the net energy balance by weighing downstream aerodynamic gains against upstream actuation losses across varying TI levels (2.0 % − 13.1 %) and pitch amplitudes (1° − 5°). Contrary to the hypothesis that high turbulence negates forced mixing, the strategy proves robust, maintaining net array power gains across all tested conditions without a restrictive ”break-even” threshold. In low-turbulence regimes ( I a = 2.0%), peak net gains reach ∼ 18 % at optimal actuation ( St ≈ 0.28). In high-turbulence regimes ( I a = 13.1%), gains persist at 2–4 %, though the location of peak energy recovery shifts upstream from x / D ≈ 3.5 to x / D ≈ 2.5. We confirm that efficacy relies on exciting specific wake instability modes ( St ≈ 0.28) rather than untargeted mixing, establishing the Helix as operationally viable even in turbulent offshore environments.