추력계수와 난류강도 변화에 따른 듀얼로터 풍력터빈 후류 특성 비교 연구

Abstract

In this study, we investigated the wake characteristics of dual-rotor wind turbines through simulations of the computational fluid dynamics (CFD) and compared the results with those of single-rotor turbines and conventional engineering wake models. Using the NREL WindSE software package based on the FEniCS project with the actuator line method, simulations were conducted for two inflow wind speeds (8 and 12 m/s) and two turbulence intensity levels (10.22% (low TI) and 14.6% (high TI)) to analyze the impact of variations in the thrust coefficient on wake behavior. The results indicated that dual-rotor systems exhibited greater velocity deficits than single-rotor turbines, with an average increase of 14.5% (low TI) and 13.8% (high TI) in the below-rated region, which was reduced to 5.8% in the above-rated region due to decreased thrust coefficients. Notably, vortex interactions between rotors caused some deflection of the centerline of the wake that was not observed in single-rotor systems. This deflection increased the contact with the freestream flow, which accelerated wake recovery rates by up to 23.1% compared with single rotors. Conventional engineering wake models (Bastankhah and Jensen Gaussian) successfully predicted overall Gaussian velocity deficit patterns but failed to capture the deflection of the centerline of the wake caused by vortex interactions. The prediction errors decreased with lower turbulence intensity and below-rated thrust coefficients, with errors increasing by a factor of approximately 1.6 in conditions with a high thrust coefficient. These findings provide fundamental quantitative data on the wake characteristics of dual-rotor wind turbines. They can also serve as a technical foundation for the optimization of the layout of wind farms and the development of specialized wake models for dual-rotor systems.