Computational Fluid Dynamics (CFD) tools are now widely used in the aerodynamic analysis of wind turbines. To simulate the turbine different modelling techniques are available with different levels of complexity and accuracy. In CFD simulations with fully resolved rotor geometries, one common approach is to resolve the blades and hub only while neglecting the supporting tower. The main advantage of this approach is that it circumvents the need to model the relative motion between rotating blades and the stationary tower. As a result, steady-state CFD simulations can be performed, and the computational resources are significantly reduced. On the other hand, however, the unsteady nature of the turbulent flow generated by the turbine blades is not properly captured, and the effects of the tower on both the near and far wakes are entirely ignored.
In the present study, the NTNU Blind Test 1 wind turbine is calculated in CFD simulations by three different approaches: 1) steady-state simulations by Absolute Formulation Method (AFM) for the rotor – only geometry; 2) unsteady simulations by Moving-Grid Formulation Method (MVG) for the rotor – only geometry; 3) unsteady simulations by MVG for the complete rotor, nacelle, and tower geometry. For all simulations, Reynolds Averaged Navier-Stokes (RANS) simulations with the k – ω SST turbulence model are performed. First, the numerical uncertainties are quantified to ensure the validity of the results. Then, for each of the configurations, the thrust coefficients (CT) and power coefficients (CP) are calculated under the inlet velocity of 10 m/s and the tip speed ratio (TSR) of 6. The wake velocity profiles are obtained, and the vortical structures from the rotor are visualized. Finally, the CFD results are compared among each other and against the measured data to provide insights into the effects of the different modeling approaches in wind turbine CFD simulations.
