Flexibility effects on airfoil noise : High-fidelity simulation and optimization

Wind turbine noise is an obstacle to the wider adoption of wind turbines: it can force the reduction, or even a halt, of wind energy production in order to comply with noise emission regulations. These effects become more severe as larger wind farms are installed. It also negatively impacts public opinion, creating barriers to the installation of new units, which may have to be placed in suboptimal locations.
The noise generated by wind turbines is a complex phenomenon, involving multiple sources and mechanisms. The dominant noise source occurs near the blade tips. The flow around the blades has a Reynolds number in the order of 107−8. The boundary layer around the blade is thus fully turbulent. While boundary layer turbulence, in itself, is not an efficient noise source when turbulent structures reach the trailing edge, the discontinuity in the flow field causes some turbulent energy to be scattered into the acoustic field. This noise-generating mechanism is called “trailing edge noise”.
Strategies to minimize trailing-edge noise include bioinspired approaches such as serrations and porosity, but these provide a limited noise reduction and reduce the aerodynamical efficiency of profiles. Another strategy is the use of flexible materials. While it has been demonstrated that flexible materials can reduce acoustic scattering at the trailing edge, the complex fluid-structure interaction has not yet been properly modeled, nor has the system been optimized. (…)

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