Physics of broadband noise reduction by serrated trailing edges

Research output: ThesisDissertation (TU Delft)

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Wind-turbine noise can restrict the growing implementation of renewable energy sources and their application close to urban environments. The largest contributor to the noise of modern turbines is the scattering of the turbulent fluctuations at the blade trailing edge. This source of noise is directly correlated with the turbine’s extracted power. Therefore, operating in noise-restricted environments and at night times entails lower energy production. An extensively applied solution for reducing the noise of wind turbines is the use of trailing-edge serrations, i.e. imposing periodic variations in the geometry of the blade trailing edge. Serrations reduce the effectiveness of the scattering at the trailing edge as the turbulent fluctuations reach the trailing edge at different times along the blade span, consequently reducing the wind-turbine noise. Although extensive literature and knowledge exist on serrations, their measured performance does not compare with the predicted one. Even more problematic, the trends predicted for the geometric alterations of the serrations are not observed in reality. Notably, two things are worth mentioning: first, geometries shown as optimal by theory perform worse than other concepts, and second, the noise from serrations is affected by the angle between the insert and the flow. As a result, the design of trailing-edge serrations still requires dedicated experiments and numerical simulations, hampering the assessment of several geometries necessary for complete optimization of the serration design. This work seeks a physical interpretation of the noise generation mechanisms of trailing edges with serrated add-ons. This interpretation is focused on understanding the underlying physical principles of the flow surrounding a serrated trailing edge. This is carried out in this work with three studies, respectively on the observation, modelling, and control of the flow and acoustic properties of serrated trailing edges...
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Delft University of Technology
  • Scarano, F., Supervisor
  • Ragni, D., Supervisor
  • Avallone, F., Advisor
Award date20 Sep 2023
Publication statusPublished - 2023


This study is supported by the SMARTANSWER project (smart mitigation of flow-induced acoustic radiation and transmission for reduced aircraft, surface transport, workplaces and wind energy noise), part of the European Union’s Horizon 2020 research and innovation programme under Marie Skłodowska-Curie grant agreement no. 722401.


  • trailing-edge noise
  • trailing-edge serrations
  • aeroacoustics
  • experimental aeroacoustics

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