Experimental Investigation and Similarity Solution of the Axisymmetric Turbulent Wake With Rotation

An experimental and analytical investigation of an axisymmetric turbulent wake with rotation was carried out. The axial and azimuthal (swirl) velocity fields were measured in the wake of a single 3-bladed model wind turbine with rotor diameter of 0.91m, up to 20 diameters downstream. The turbine was positioned in the free stream, near the entrance of the 6 m × 2.7 m cross section of the UNH Flow Physics Facility. Measurements were conducted at different rotor loading conditions with blade tip-speed ratios from 2.0 to 2.8. A pitot-static tube and constant temperature hot-wire anemometry with a multi-wire sensor were used to measure velocity fields. An equilibrium similarity theory for the turbulent axisymmetric wake with rotation was outlined, and first evidence for a new scaling function for the decay of the mean swirling velocity component, W_max ∝ x⁻¹ ∝ $Uo3/2$⁠, was found.