Volumetric three-dimensional experimental measurement of vortex dynamics in a rotating wake
Phys. Rev. Fluids 11, 014701 – Published 8 January, 2026
DOI: https://doi.org/10.1103/9pwb-ky8n
Abstract
The wake of a model wind turbine was experimentally investigated to better understand the dynamics of tip, hub, and tower vortices and their interactions. The free-spinning two-blade model turbine was positioned in a turbulent freestream flow downstream of an active grid, resulting in a tip speed ratio of approximately 4. Volumetric particle tracking velocimetry was used to capture the full near-field wake, up to three rotor diameters downstream of the turbine, and the vortex structures are described in terms of the phase-averaged vorticity and Lamb vectors. A detailed characterization was made in the tip vortex frame of reference by studying the evolution of the circulation, size, and orientation of the structures with downstream distance. The two tip vortices shed from each blade have different circulation magnitudes and merge around 1.5 rotor diameters downstream of the turbine, resulting in changes to the characteristics of the stronger vortex. After merging, the tip vortex is more elliptical, its local orientation is different, and its circulation begins to decay more rapidly. Finally, the positional scatter of instantaneous tip vortices and their development with downstream distance are quantified to explain the decreasing circulation of the phase-averaged structures downstream.
