Parametric guidance for turbulent noise reduction from poroelastic trailing edges and owls

2013 ◽  
Author(s):  
Justin Jaworski ◽  
Nigel Peake
Keyword(s):  
Noise Reduction ◽  
Trailing Edges

scholarly journals Role of Polymeric Coating on Metallic Foams to Control the Aeroacoustic Noise Reduction of Airfoils with Permeable Trailing Edges

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1087 ◽  
Author(s):  
Reza Hedayati ◽  
Alejandro Rubio Carpio ◽  
Salil Luesutthiviboon ◽  
Daniele Ragni ◽  
Francesco Avallone ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Metal Foams ◽  
Polymeric Coating ◽  
Metallic Foams ◽  
Noise Mitigation ◽  
Trailing Edge ◽  
Reference Case ◽  
Pore Sizes ◽  
Coated Metal ◽  
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, a step to control the aeroacoustics effect of such porous trailing edges is taken, by applying a polymeric coating onto the internal foam structure. Using this method, the internal topology of the foam is maintained, but its permeability is significantly affected. This study opens a new possibility of aeroacoustic control, since the polymeric coatings are temperature responsive, and their thickness can be controlled inside the foam. Porous metallic foams with pore sizes of 580, 800, and 1200 μm are (internally) spray-coated with an elastomeric coating. The uncoated and coated foams are characterized in terms of reduced porosity, average coating thickness and air-flow resistance. Subsequently, the coated and uncoated foams are employed to construct tapered inserts installed at the trailing edge of an NACA 0018 airfoil. The noise mitigation performances of the coated metal foams are compared to those of uncoated metal foams with either similar pore size or permeability value, and both are compared to the solid trailing edge reference case. Results show that that the permeability of the foam can be easily altered by the application of an internal coating on the metallic foams. The noise reduction characteristics of the coated foams are similar to equivalent ones with metallic materials, provided that the coating material is rigid enough not to plastically deform under flow conditions.

scholarly journals On the mechanisms of jet-installation noise reduction with flow-permeable trailing edges

2021 ◽  
pp. 116582
Author(s):  
Leandro Rego ◽  
Francesco Avallone ◽  
Daniele Ragni ◽  
Damiano Casalino
Keyword(s):  
Noise Reduction ◽  
Trailing Edges

Experimental Study on Noise Reduction Using Brush-Serrated Trailing Edges

2019 ◽  
Author(s):  
Yong Wang ◽  
Dao-feng Tang ◽  
Kun Zhao ◽  
Wen-Jian Li ◽  
Ben Huang
Keyword(s):  
Experimental Study ◽  
Noise Reduction ◽  
Trailing Edges

scholarly journals Prediction of noise from serrated trailing edges

2016 ◽  
Vol 793 ◽  
pp. 556-588 ◽  
Author(s):  
B. Lyu ◽  
M. Azarpeyvand ◽  
S. Sinayoko
Keyword(s):  
Noise Reduction ◽  
Analytical Model ◽  
Leading Edge ◽  
Experimental Investigations ◽  
Destructive Interference ◽  
Trailing Edge ◽  
Trailing Edges ◽  
Mach Numbers ◽  
Trailing Edge Serrations ◽  
High Mach

A new analytical model is developed for the prediction of noise from serrated trailing edges. The model generalizes Amiet’s trailing-edge noise theory to sawtooth trailing edges, resulting in a complicated partial differential equation. The equation is then solved by means of a Fourier expansion technique combined with an iterative procedure. The solution is validated through comparison with the finite element method for a variety of serrations at different Mach numbers. The results obtained using the new model predict noise reduction of up to 10 dB at 90$^{\circ }$ above the trailing edge, which is more realistic than predictions based on Howe’s model and also more consistent with experimental observations. A thorough analytical and numerical analysis of the physical mechanism is carried out and suggests that the noise reduction due to serration originates primarily from interference effects near the trailing edge. A closer inspection of the proposed mathematical model has led to the development of two criteria for the effectiveness of the trailing-edge serrations, consistent but more general than those proposed by Howe. While experimental investigations often focus on noise reduction at 90$^{\circ }$ above the trailing edge, the new analytical model shows that the destructive interference scattering effects due to the serrations cause significant noise reduction at large polar angles, near the leading edge. It has also been observed that serrations can significantly change the directivity characteristics of the aerofoil at high frequencies and even lead to noise increase at high Mach numbers.

Airfoil Self-Noise Reduction by Gradient Distributed Porous Trailing Edges

2021 ◽  
Vol 34 (6) ◽  
pp. 04021075
Author(s):  
Yong Wang ◽  
Nan-Song Hao ◽  
Xiang-Yu Lu ◽  
Fan Tong ◽  
Yu-Bao Song
Keyword(s):  
Noise Reduction ◽  
Trailing Edges ◽  
Airfoil Self Noise

Jet noise reduction of spherical tuyeres with serrated trailing edges

2021 ◽  
Vol 44 ◽  
pp. 103324
Author(s):  
Chi Zhang ◽  
Angui Li ◽  
Jinnan Guo ◽  
Haimeng Li ◽  
Jigang Che ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Jet Noise ◽  
Trailing Edges

Noise reduction and aerodynamics of isolated multi-copter rotors with serrated trailing edges during forward flight

2020 ◽  
Vol 489 ◽  
pp. 115688
Author(s):  
Yannian Yang ◽  
Yong Wang ◽  
Yu Liu ◽  
Haitao Hu ◽  
Zhiyong Li
Keyword(s):  
Noise Reduction ◽  
Forward Flight ◽  
Trailing Edges
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