06 May 2022
06 May 2022
Status: this preprint is currently under review for the journal WES.

Atmospheric rotating rig testing of a swept blade tip and comparison with multi-fidelity aeroelastic simulations

Thanasis Barlas, Georg Raimund Pirrung, Néstor Rámos-García, Sergio González Horcas, Ang Li, and Helge Aagaard Madsen Thanasis Barlas et al.
  • DTU Wind Energy, Frederiksborgvej 399, 4000 Roskilde, Denmark

Abstract. One promising design solution for increasing the energy production of modern horizontal axis wind turbines is the installation of curved tip extensions. However, since the aeroelastic response of such geometrical add-ons has not been characterized yet, there are currently uncertainties in the application of traditional aerodynamic numerical models. The objective of the present work is twofold. On the one hand, it represents the first effort in the experimental characterization of curved tip extensions in atmospheric flow. On the other hand, it includes a comprehensive validation exercise, accounting for different numerical models for aerodynamic loads prediction. The experiments consist of controlled field tests in the outdoor rotating rig at the Risø campus of the Technical University of Denmark (DTU), and consider a swept tip shape. This geometry is the result of an optimized design, focusing on locally maximizing power performance within load constraints compared to an optimal straight tip. The tip model is instrumented with spanwise bands of pressure sensors and is tested in atmospheric inflow conditions. A range of fidelity of aerodynamic models is then utilized to aeroelastically simulate the test cases and to compare with the measurement data. Those aerodynamic codes include a blade element momentum (BEM) method, a vortex-based method coupling a near-wake model with a far-wake model (NW), a lifting-line hybrid wake model (LL) and fully resolved Navier-Stokes computational fluid dynamics (CFD) simulations. Results show that the measured mean normal loading can be captured well with the vortex-based codes and the CFD solver. The observed trends in mean loading are in good agreement with previous wind tunnel tests of a scaled and stiff model of the tip extension. The CFD solution shows a highly three-dimensional flow at the very outboard part of the curved tip that leads to large changes of the angle of the resultant force with respect to the chord. Turbulent simulations using the BEM code and the vortex codes resulted in a good match with the measured standard deviation of the normal force, with some deviations of the BEM results due to the missing root vortex effect.

Thanasis Barlas et al.

Status: open (until 17 Jun 2022)

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Thanasis Barlas et al.

Thanasis Barlas et al.


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Short summary
An aeroelastically optimized curved wind turbine blade tip is designed, manufactured and tested on a novel outdoor rotating rig facility at the Risø campus of the Technical University of Denmark. Detailed aerodynamic measurements for various atmospheric conditions and results are compared to a series of in-house aeroelastic tools with a range of fidelity in aerodynamic modelling. The comparison highlights the details in the ability of the codes to predict the performance of such a curved tip.