Modern aerodynamics is responding to the world energy-crisis with the creation of the largest machines on Earth. Among many examples, large wings/blades are optimized to harvest energy from the wind (e.g. wind turbines) or to decrease fuel mass spent per payload (e.g. aircraft and propellers). Improving performance through upscaling comes with a huge increase of aeroacoustic noise, which directly affects
the health of human population, as well as it obliges wind-turbine manufacturers and airports to restrict the operating envelope of wind-turbines and airplanes. Noise of wings or blades, “airfoil self-noise”, is either generated by the interaction of the incoming flow with the airfoil leading-edge or of the turbulent boundary-layer with the airfoil trailing-edge. State-of-the-art mitigation-strategies involve a substantial modification of the geometry, often with “a-posteriori” installation of additional devices, which narrow the range of operating conditions. The research of this STW project aims at the abatement of airfoil self-noise, with a new flow-porous material constituted by “open foams with directional cavities”. This revolutionary concept allows shaping the macro characteristics (edge geometry, angles) of conventional passive noise-reduction techniques, into the micro ones of the porous structure (porosity, cavity orientation), towards the creation of a material able to mitigate noise by both dampening flow fluctuations and reducing acoustic scattering. Addressing both hydrodynamic and acoustic aspects of noise is extremely challenging due to the different flow-scales and physical mechanisms involved. The proposed research aims at studying, designing and prototyping inserts for wind-tunnel wings with open foams able to work at a multi-scale level. Flow features will be studied to shape the optimal flow path for noise mitigation in the material. The study will focus on the following relevant noise sources in aeroacoustics:

1. abatement of turbulent boundary-layer trailing-edge noise in wind turbine blades;
2. abatement of flap-side and leading-edge noise in aircraft wings