Characterisation of a horizontal axis wind turbine’s tip and root vortices

• Published in: Experiments in fluids Vol. 54; no. 3
• Main Authors: Sherry, Michael, Sheridan, John, Jacono, David Lo
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.03.2013; Springer
• Subjects: Applied sciences; Energy; Engineering; Engineering Fluid Dynamics; Engineering Thermodynamics; Exact sciences and technology; Fluid dynamics; Fluid- and Aerodynamics; Fundamental areas of phenomenology (including applications); Heat and Mass Transfer; Instrumentation for fluid dynamics; Natural energy; Physics; Research Article; Wind energy; Horizontal Axis Wind Turbine; Wind Turbine; Vortex; Laminar Separation Bubble; Separate Shear Layer; Swirling flow; Laser induced fluorescence; Speed measurement; Aerodynamics; Wind generator; Experimental study; Horizontal axis; End vortex; Near wake; Test facility; Flow visualization; Particle image velocimetry; Model test
• ISSN: 0723-4864; 1432-1114
• DOI: 10.1007/s00348-012-1417-y

The vortical near wake of a model horizontal axis wind turbine has been investigated experimentally in a water channel. The objective of this work is to study vortex interaction and stability of the helical vortex filaments within a horizontal axis wind turbine wake. The experimental model is a geometrically scaled version of the Tjæreborg wind turbine, which existed in western Denmark in the late 1980s. Here, the turbine was tested in both the upwind and downwind configurations. Qualitative flow visualisations using hydrogen bubble, particle streakline and planar laser-induced fluorescence techniques were combined with quantitative data measurements taken using planar particle image velocimetry. Vortices were identified using velocity gradient tensor invariants. Parameters that describe the helical vortex wake, such as the helicoidal pitch, and vortex circulation, were determined for three tip speed ratios. Particular attention is given here to the root vortex, which has been investigated minimally to date. Signatures of the coherent tip vortices are seen throughout the measurement domain; however, the signature of the root vortex is only evident much closer to the rotor plane, irrespective of the turbine configuration. It is postulated that the root vortex diffuses rapidly due to the effects of the turbine support geometries.