Preprints
https://doi.org/10.5194/wes-2021-115
https://doi.org/10.5194/wes-2021-115

  01 Nov 2021

01 Nov 2021

Review status: this preprint is currently under review for the journal WES.

CFD-based curved tip shape design for wind turbine blades

Mads Holst Aagaard Madsen1, Frederik Zahle1, Sergio González Horcas1, Thanasis Barlas2, and Niels Nørmark Sørensen1 Mads Holst Aagaard Madsen et al.
  • 1Aero- and Fluid Dynamics (AFD) section, DTU Wind Energy, Lyngby Campus, Nils Koppels Allé, building 403, 2800 Lyngby, Denmark
  • 2Airfoil and Rotor Design (ARD) section, DTU Wind Energy, Risø Campus, Frederiksborgvej 399, 4000 Roskilde, Denmark

Abstract. This work presents a high-fidelity shape optimization framework based on computational fluid dynamics (CFD). The presented work is the first comprehensive curved tip shape study of a wind turbine rotor to date using a direct CFD-based approach. Preceeding the study is a thorough literature survey particularly focused on wind turbine blade tips in order to place the present work in its context. Then follows a comprehensive analysis to quantify mesh dependency and to present needed mesh modifications ensuring a deep convergence of the flow field at each design iteration. The presented modifications allow the framework to produce up to 6 digit accurate finite difference gradients which are verified using the machine accurate Complex-Step method. The accurate gradients result in a tightly converged design optimization problem where the studied problem is to maximize power using 12 design variables while satisfying constraints on geometry as well as on the bending moment at 90 % blade length. The optimized shape has about 1 % r/R blade extension, 2 % r/R flapwise displacement, and slightly below 2 % r/R edgewise displacement resulting in a 1.12 % increase in power. Importantly, the inboard part of the tip is de-loaded using twist and chord design variables as the blade is extended ensuring that the baseline steady-state loads are not exceeded. For both analysis and optimization an industrial scale mesh resolution of above 14 · 106 cells is used which underlines the maturity of the framework.

Mads Holst Aagaard Madsen et al.

Status: open (until 25 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on wes-2021-115', Malo Rosemeier, 05 Nov 2021 reply
    • AC1: 'Reply on CC1', Mads H. Aa. Madsen, 09 Nov 2021 reply

Mads Holst Aagaard Madsen et al.

Mads Holst Aagaard Madsen et al.

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Short summary
This work presents a shape optimization framework based on computational fluid dynamics. The design framework is used to optimize wind turbine blade tips for maximum power increase while avoiding that extra loading is incurred. The final results are shown to align well with a related literature. The resulting tip shape, could be mounted on already installed wind turbines as a sleeve-like solution, or be conceived as part of a modular blade with tips designed for site-specific conditions.