Preprints
https://doi.org/10.5194/wes-2021-48
https://doi.org/10.5194/wes-2021-48

  27 May 2021

27 May 2021

Review status: a revised version of this preprint was accepted for the journal WES and is expected to appear here in due course.

Wind tunnel testing of a swept tip shape and comparison with multi-fidelity aerodynamic simulations

Thanasis Barlas, Georg Raimund Pirrung, Néstor Ramos-García, Sergio González Horcas, Robert Flemming Mikkelsen, Anders Smærup Olsen, and Mac Gaunaa Thanasis Barlas et al.
  • DTU Wind Energy, Frederiksborgvej 399, 4000 Roskilde, Denmark

Abstract. One promising design solution for increasing the efficiency of modern horizontal axis wind turbines is the installation of curved tip extensions. However, introducing such complex geometries may move traditional aerodynamic models based on Blade Element Momentum (BEM) theory out of their range of applicability. This motivated the present work, where a swept tip shape is investigated by means of both experimental and numerical tests. The latter group accounted for a wide variety of aerodynamic models, allowing to highlight the capabilities and limitations of each of them in a relative manner. The considered swept tip shape is the result of a design optimization, focusing on locally maximizing power performance within load constraints. For the experimental tests, the tip model is instrumented with spanwise bands of pressure sensors and is tested in the Poul la Cour wind tunnel at the Technical University of Denmark (DTU). The methods used for the numerical tests consisted of a blade element model, a near-wake model, lifting-line free-wake models, and a fully resolved Navier- Stokes solver. The comparison of the numerical and the experimental tests results is performed for a given range of angles of attack and wind speeds, which is representative of the expected conditions in operation. Results show that the blade element model cannot predict the measured normal force coefficients, but the other methods are generally in good agreement with the measurements in attached flow. Flow visualization and pressure distribution compare well with Computational Fluid Dynamics (CFD) simulations. The agreement in the clean case is better than in the tripped case, indicating an aggressive tripping of the flow in the measurements. Some uncertainties regarding the effect of the boundary layer at the inboard tunnel wall and the post stall behavior remain.

Thanasis Barlas et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wes-2021-48', Joerg Alber, 23 Jun 2021
  • RC2: 'Comment on wes-2021-48 - Reviewer', Anonymous Referee #2, 16 Jul 2021
  • AC1: 'Review response on wes-2021-48-RC1/RC2', Athanasios Barlas, 06 Aug 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wes-2021-48', Joerg Alber, 23 Jun 2021
  • RC2: 'Comment on wes-2021-48 - Reviewer', Anonymous Referee #2, 16 Jul 2021
  • AC1: 'Review response on wes-2021-48-RC1/RC2', Athanasios Barlas, 06 Aug 2021

Thanasis Barlas et al.

Thanasis Barlas et al.

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Short summary
Curved blade tips can potential have a significant inpact on wind turbine performance and loads. A swept tip shape, optimized for wind turbine applications is tested in a wind tunnel. A range of numerical aerodynamic simualtion tools with various levels of fidelity is compared. It is shown that all numerical tools except for the simplest BEM-based are in good agreement with the measurements, suggesting the required level of model fidelity necessary for the design of such tips.