11th ANKARA INTERNATIONAL AEROSPACE CONFERENCE, Ankara, Turkey, 8 - 10 September 2021, pp.1-25
In this paper, wake shapes of wind turbine rotors are investigated by using CFD and analytical wake models. The flow around the NTNU model turbine is simulated using the Reynolds-Averaged Navier-Stokes Equations with Spalart-Allmaras, standard k-epsilon, standard k-omega, and k-omega SST turbulence models, k-kL-omega and Transition SST transition models and also with two different freestream turbulence intensities as low and high values of 0.23% and 10%, respectively. The simulations are done for a single turbine and then for two aligned turbines, one behind another. The wake velocity profile results obtained from the CFD simulations at different downstream locations are compared with the available experimental measurements and with the calculated analytical wake model results and also among each other. The results show that CFD tools are necessary to investigate the unsymmetrical wake shape near the rotor. However, the wake models may predict the average flow speed away from the turbine well. Moreover, the models developed with detailed methods can predict the velocity profiles much better in shape, especially when there is a high turbulence level in the flow. Moreover, the two-turbine case results from the wake models show that the wake superposition method could significantly impact the velocity distribution within a wind farm.