Quantitative criteria to design optimal permeable trailing edges for noise abatement

An experimental study on broadband noise scattered by permeable trailing edges with different pore arrangements is performed. A NACA 0018 airfoil with chord c = 0.2 m is investigated at chord-based Reynolds numbers ranging from 1.4 × 10⁵ to 3.8 × 10⁵ and angles of attack of 0.2 and 5.4 degrees. Noise emission from five...

Mechanisms of broadband noise generation on metal foam edges

The turbulent flow over a porous trailing edge of a NACA 0018 airfoil is experimentally investigated to study the link between the hydrodynamic flow field and the acoustic scattering. Four porous trailing edges, obtained from open-cell metal foams, are tested to analyze the effects on far-field noise of the permeability of the material and of...

Experimental characterization of the turbulent boundary layer over a porous trailing edge for noise abatement

The hydrodynamic and acoustic fields for a NACA 0018 with solid and porous trailing edge inserts are investigated. The porous inserts, covering 20% of the chord, are manufactured with metal foams with cell diameters of 450 and 800 μm and permeability values of 6 × 10−10 and 2.7 × 10−9 m2. The experiments are performed at a chord-based Reynolds...

Role of polymeric coating on metallic foams to control the aeroacoustic noise reduction of airfoils with permeable trailing edges

Studies on porous trailing edges, manufactured with open-cell Ni-Cr-Al foams with sub-millimeter pore sizes, have shown encouraging results for the mitigation of turbulent boundary-layer trailing-edge noise. However, the achieved noise mitigation is typically dependent upon the pore geometry, which is fixed after manufacturing. In this study,...