Physics of broadband noise reduction by serrated trailing edges

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...

A parametric study of serration design for trailing–edge broadband noise reduction

This work discusses the physics of noise reduction achieved from serrated trailing–edges and its impact by the serration design. An experimental campaign is carried out with a benchmark 2D model based on a NACA 63₃–018 airfoil. Different trailing-edge serrations are tested under several flow speeds and angles of attack conditions...

Turbulent-boundary-layer trailing-edge noise reduction technologies including porous materials

Noise reduction is one of the major challenges to the societal acceptance of wind turbines. Aerodynamic noise sources are the dominant ones, assuming that mechanical noise can be reduced by correct insulation and periodic maintenance of the gearbox and drive train and by adding insulating material in the wind-turbine nacelle. The dominant...

Assessing and improving trailing-edge noise reduction technologies for industrial wind-turbine applications

Nowadays, large wind turbines are installed and operated close to densely populated areas due to the growing need for renewable energy. Noise constraints are hampering this development. The most relevant wind turbine noise source is the so-called Turbulent Boundary Layer Trailing-Edge (TBL–TE) noise. Many passive TBL–TE noise reduction...

Aeroacoustics of sawtooth trailing-edge serrations under aerodynamic loading

The impact of aerodynamic loading on a serrated trailing edge is studied experimentally. Aerodynamic and acoustic measurements are conducted on a sawtooth-shaped trailing edge, retrofitted to a flat plate featuring a trailing-edge flap, and placed at incidence to the free-stream flow. The turbulent flow across the trailing edge is inspected...

Holistic approach to wind turbine noise: From blade trailing-edge modifications to annoyance estimation

Wind turbines represent an encouraging option for sustainable energy but their noise emissions can be an issue for their public acceptance. Noise reduction measures, such as trailing-edge serrations or permeable inserts, seem to offer promising results in reducing wind turbine noise levels. This manuscript presents a novel holistic approach...

Trailing-edge serrations effect on the performance of a wind turbine

An experimental study focusing on the change of the aerodynamic performance of a wind turbine with the employment of trailing-edge serrations is presented. The design procedure which starts from the serration design, together with the experimental wind tunnel testing and the installation in an already operating wind turbine is discussed. A...

Assessment of the sound quality of wind turbine noise reduction measures

Noise emissions from wind turbines are one of the main issues that the wind energy industry must deal with nowadays. Strict noise regulations often prevent wind turbines to operate at maximum power conditions, causing large losses of power production and, hence, of revenue. Several noise reduction measures have been proposed so far, but the...

Trailing edge serrations effects on the aerodynamic performance of a NACA 643418

A study of the aerodynamic performance of a NACA 643418 airfoil with trailing edge serrations is presented. For the prediction of the changes in lift due to the serration installation, an empirical law is derived that can be extended to typical cambered airfoils for wind turbine applications. The law is deduced from 2D and 3D Reynolds‐averaged...

Effect of trailing edge serration-flow misalignment on airfoil noise emissions

The broadband noise generated by the scattering of turbulent flow at the trailing edge of a NACA 0018 airfoil with trailing edge serrations is investigated, varying both the airfoil angle of attack and serration flap angle. Acoustic emissions from the trailing edge are measured using a microphone array. The noise level is observed to be...

A study on the near-surface flow and acoustic emissions of trailing edge serrations: For the purpose of noise reduction of wind turbine blades

The flow near the surface, and the acoustic emissions of trailing edge serrations are investigated in this work. The use of this family of aerodynamic devices on airfoils is intended for the reduction of turbulent boundary layer-trailing edge noise (TBL-TE noise). This purpose has been well demonstrated in wind tunnel and numerical experiments....

Acoustic Emissions of Semi-Permeable Trailing Edge Serrations

The trailing edge of a NACA 0018 airfoil is modified through the attachment of serrations with different degrees of permeability. Acoustic beamforming is used to inspect the turbulent boundary layer-trailing edge noise emissions from the unmodified and serrated trailing edges. Different freestream velocities and angles of attack are investigated...

Benefits of curved serrations on broadband trailing-edge noise reduction

Far-field noise and flow field over a novel curved trailing-edge serration (named as iron-shaped serration) are investigated. Spectra of the far-field broadband noise, directivity plots and the flow-field over the iron-shaped serration are obtained from numerical computations performed using a compressible Lattice-Boltzmann solver. The new...

Computational aeroacoustic analysis of trailing edge noise: A Direct Numerical Simulation using the Lattice Boltzmann Method

To investigate the mechanisms of wing trailing edge noise the aeroacoustic sound generation by a NACA 0018 has been computed with direct numerical simulations using the Lattice Boltzmann Method. Noise from the straight trailing edge wing is compared with the sound generated by a sawtooth serrated wing, which reduces the noise emission according...