A Comparison of Wind Turbine and Porous Disk Wakes at High Reynolds Numbers*

The present study examines the suitability of the actuator disk wind turbine model at field-relevant Reynolds numbers through an experimental comparison between the wakes of a three-bladed horizontal axis wind turbine and a matched porous disk. The experiments are conducted in the High Reynolds Test Facility at Princeton University, where high Reynolds numbers are achieved at flow velocities less than 10 m/s using air pressurized up to 238 bar as the working fluid. The rotor (18% solidity) and disk are matched in terms of diameter (20 cm) and radial solidity distribution, with the solidity of the disk varied between 30% and 60% to match rotor thrust coefficients at diameter-based Reynolds numbers of 3×10⁶ to 7×10⁶ and tip speed ratios of 3.5 to 6. Wake measurements are performed using nanoscale thermal anemometry, capturing the mean and time-varying structure of the both the near and far wakes. Particular attention is paid to the near wake, where differences are noted on account of wake dynamics driven by tip vortex and shear layer development in the rotor and disk cases, respectively. Results are compared with previous findings at much lower Reynolds numbers, leading to conclusions on the suitability of the actuator disk model at high Reynolds numbers.