Aerodynamic Performance and Wake Characteristics of a Four-Rotor Wind Turbine

The continuous upscaling of offshore wind turbines exacerbates challenges such as blade flutter, stability degradation, and logistical difficulties. To address these issues, this study proposes a parallel multi-rotor wind turbine and systematically investigates its aerodynamic performance and wake characteristics. Based on a 5 MW reference turbine, validated Unsteady Reynolds-Averaged Navier–Stokes (URANS) simulations incorporating the sliding mesh technique and Shear Stress Transport (SST) k-ω turbulence model are conducted to evaluate twin- and four-rotor configurations under various geometric and rotational layouts. Crucially, this study reveals for the first time that asymmetric rotational configurations induce wind field skewness and modify rotor-edge bypass flow, leading to power imbalance among rotors. Additionally, the twin-rotor configuration enhances total power output with negligible thrust variation. For the four-rotor system, power is highly spacing-dependent: at 1.1 rotor diameter spacing, power increases by approximately 3.0% compared to a single rotor. As spacing increases, rotor coupling weakens, which reduces wake non-uniformity but simultaneously slows wake recovery and decreases power generation.