2-D RANS approach for H-darrieus rotors power prediction: developing efficient and accurate methodology across broad geometrical configurations and operating conditions

This study aims to develop a comprehensive CFD methodology to accurately predict the Power Coefficient (CP) across a wide range of rotor solidities (σ) and Tip Speed Ratios (TSR) for small-size H-Darrieus wind turbines. The methodology involved delineating the characteristic curve by simulating only three key operating points based on useful power-producing operating condition limits: TSRin, TSRr, and TSRout, for five case studies from the literature, covering solidities from 0.12 to 0.75. The TSRr, representing the TSR of the turbine’s rated operating point, is estimated by using an empirical correlation from the literature which provides the TSRr magnitude solely based on σ. TSRin and TSRout are then calculated as defined percentages of TSRr. The methodology was validated against experimental data from the literature, yielding root-mean-square errors below 0.05 for CP at any TSR within the key operating points. Additionally, a minimum number of revolutions required for simulation convergence of each σ at each TSR were established, as well as, by using dimensionless parameters to assess spatio-temporal discretization, general recommendations for mesh and time step resolutions, for rotors with 0.12 ≤ σ ≤ 0.75, operating within TSRin < TSR < TSRout. Finally, a CFD workflow has been developed to provide reliable H-Darrieus simulations, achieving reductions of up to threefold in total simulation time.