Development and wind tunnel testing of a low-cost secondary windscreen for wind turbine field measurements

Kurzfassung

This study investigates the development and wind tunnel testing of a low-cost secondary windscreen for reducing acoustic interference in wind turbine field measurements. Six different secondary windscreens were designed and fabricated, including fabric and foam versions, and compared in terms of their acoustic insertion losses and wind-induced self-noise. Tests in an anechoic chamber showed low acoustic insertion losses for all mesh and foam windscreens, while the fabric demonstrated variable results. Wind tunnel tests revealed that mesh and foam secondary windscreens effectively reduced wind-induced self-noise. All results are compared to an off-the-shelf secondary windscreen from Microtech Gefell (MG). The best windscreen from metal construction and fine mesh coating reduces wind induced self-noise by up to 5 dB for frequencies greater than 400 Hz when compared to using only a primary windscreen. For some cases, the shallow design of the self-made windscreen performed better than the MG. By a scaling of spectra, it showed that the mesh of the MG windscreen may introduce low frequency surface vibrations as well as dipole sound sources from the edges of the wireframe. All other screens are dominated by sources from the free turbulent wake.