On the Scaling of Wind Turbine Rotors

Pietro Bortolotti, Helena Canet, Carlo Bottasso

Research output: Contribution to journalArticlepeer-review

20 Scopus Citations


This paper formulates laws for scaling wind turbine rotors. Although the analysis is general, the article primarily focuses on the subscaling problem, i.e., on the design of a smaller-sized model that mimics a full-scale machine. The present study considers both the steady-state and transient response cases, including the effects of aerodynamic, elastic, inertial, and gravitational forces. The analysis reveals the changes to physical characteristics induced by a generic change of scale, indicates which characteristics can be matched faithfully by a subscaled model, and states the conditions that must be fulfilled for desired matchings to hold./p pBased on the scaling laws formulated here, the article continues by considering the problem of designing scaled rotors that match desired indicators of a full-scale reference. To better illustrate the challenges implicit in scaling and the necessary tradeoffs and approximations, two different approaches are contrasted. The first consists in a straightforward geometric zooming. An analysis of the consequences of zooming reveals that, although apparently simple, this method is often not applicable in practice, because of physical and manufacturing limitations. This motivates the formulation of scaling as a constrained optimal aerodynamic and structural matching problem of wide applicability./p pPractical illustrations are given considering the scaling of a large reference 10 MW wind turbine of about 180 m in diameter down to three different sizes of 54, 27, and 2.8 m. Results indicate that, with the proper choices, even models characterized by very significant scaling factors can accurately match several key performance indicators. Additionally, when an exact match is not possible, relevant trends can at least be captured./p.

Original languageAmerican English
Pages (from-to)601-626
Number of pages26
JournalWind Energy Science
Issue number3
StatePublished - 2021

Bibliographical note

See NREL/JA-5000-76386 for article as published in Wind Energy Science Discussions

NREL Publication Number

  • NREL/JA-5000-80125


  • design optimization
  • field testing
  • rotor design
  • scaling
  • wind tunnel


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