Noise reduction mechanisms of an open-cell metal-foam trailing edge

Abstract

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Aerodynamic noise from an asymmetric airfoil with perforated extension plates at the trailing edge

“…Further, the M0 model airfoil results in an acoustic scattering at the trailing edge due to the sudden impedance mismatch similar to that of the base airfoil. 40 An increase in the pore diameter leads to a gradual decrease in the low frequency noise below ∼ 1.5 kHz (Figure 8) due to a decrease in the surface impedance of the airfoil models from M1 to M4. This indicates that the perforations reduce the turbulent fluctuations, thus reducing the low frequency noise.…”

On the noise reduction of a porous trailing edge applied to an airfoil at lifting condition

“…22,23 In a different approach, referred to as the volume-averaging method, the internal volume of the porous medium is replaced by an equivalent fluid region, where additional physical conditions are imposed to take the porous media properties (e.g., permeability and porosity) into account. 11,24 This technique has been employed previously by the authors 14 for studying a National Advisory Committee for Aeronautics (NACA) 0018 equipped with a metal-foam TE insert, replicating the experimental setup of Rubio Carpio et al 10 They concluded that, in addition to the smoother impedance transition at the TE, the destructive interference between the noise emitted by the distributed sound sources on the porous insert contributed toward noise attenuation.…”

“…[9][10][11] Permeable TE inserts, in particular, have been demonstrated to be promising passive noise mitigation devices due to their ability to produce substantial noise reduction, with relatively small adverse aerodynamic impact. [12][13][14][15] These inserts tend to produce larger noise reduction when materials with higher permeability and porosity are employed, although this comes at the cost of aerodynamic penalty. 9 Nevertheless, it is necessary to understand the underlying principles of the porous inserts in order to better optimize their applications.…”

Charpy Impact Behavior of a Novel Stainless Steel Powder Wire Mesh Composite Porous Plate

“…They have the advantages of low density, high temperature resistance, controllable pore structure, high specific strength, large specific surface area, and machinability [ 1 ]. They are widely used in filtration [ 2 , 3 , 4 ], heat dissipation [ 5 , 6 , 7 ], noise reduction [ 8 , 9 , 10 , 11 ], medical treatment [ 12 , 13 , 14 ], catalysis [ 15 , 16 , 17 , 18 ], and other fields. With the continuous development of porous metal materials, they are not only used as an excellent functional material, but also as a structural material in the situation of complex stress, especially in the situation of impact load, such as the energy absorption and anticollision structure in the automotive field [ 19 ], which puts forward higher requirements for the impact performance of materials.…”