Turbulent wakes generated by 1 m diameter wind turbinemodels*

The turbulent wakes generated by two 1 m diameter wake generator models were studied in the Flow Physics Facility (FPF) at the University of New Hampshire. The FPF has a cross section of 6.0m (W) x 2.7m (H), resulting in a blockage ratio of less than 5%. Horizontal and vertical velocity profiles were measured downstream of a 1 m porous disk up to 50 m downstream. The disk wake elongates in the vertical direction as it evolves far downstream, due to influence of wall boundary layers, and shifts downward due to the presence of the wind turbine model tower. Streamwise and azimuthal velocity profiles were measured in the wake of a 1 m diameter scale model wind turbine to 20 diameters downstream. The mean swirl appears to decouple from the mean velocity deficit as the wake evolves downstream; however, the mean azimuthal velocity W still exhibits a W∼x^-1∼U_o^3/2 scaling at intermediate downstream locations, where U_o is the wake centerline velocity deficit.  Both disk and wind turbine wakes exhibit the classical high-Reynolds number scaling for axisymmetric turbulent wakes up to 20 diameters downstream. Axial and angular momentum integrals demonstrate that the mean pressure gradient is non-negligible in the near wake.