Experimental study of mean and turbulent velocity fields in the wake of a twin-rotor vertical axis wind turbine

• Published in: Journal of physics. Conference series Vol. 2265; no. 2; pp. 22073 - 22082
• Main Authors: van der Deijl, W., Obligado, M., Sicot, C., Barre, S.
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.05.2022
• Subjects: Aerodynamics; Aspect ratio; Particle image velocimetry; Physics; Recovery; Rotors; Turbulence intensity; Velocity distribution; Vertical axis wind turbines; Wind tunnels
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/2265/2/022073

Abstract The wake of a twin-rotor vertical axis wind turbine (VAWT) was measured experimentally in a wind tunnel using particle image velocimetry. Only the horizontal centre plane was measured, showing that there is no wake recovery in this central plane. The wake deficit in this plane actually increases up to x = 5.5 D , independent of tip-speed-ratio. The wake of a VAWT is, therefore, not homogeneous but three-dimensional. Which also means that the aspect ratio of a VAWT is an important parameter if one wants to optimise for wake recovery. In addition, the shed vortices at the edge of the wake do not play a role in the wake recovery. They do not enhance the recovery, nor do they shield the wake from re-energising. A reason for this is that their persistence strongly depends on tip-speed-ratio yet them breaking down has no effect on the wake recovery. Furthermore, the turbulence intensity levels at the edge of the wake are relatively low and often lower than the centre part of the wake. Hence, the dominant process of wake recovery of a VAWT must be happening in the vertical plane, which is in correspondence with previous research.