Diffraction Effects on the Trailing Edge Noise Meaasured in an Open-Jet Anechoic Wind Tunnel

2007 ◽  
Author(s):  
Stephane Moreau ◽  
Christophe Schram ◽  
Michel Roger
Keyword(s):  
Wind Tunnel ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Diffraction Effects

Experimental investigation of porous materials for trailing-edge noise reduction

2020 ◽  
Vol 19 (6-8) ◽  
pp. 365-384
Author(s):  
K-S Rossignol ◽  
A Suryadi ◽  
M Herr ◽  
J Schmidt ◽  
J Tychsen
Keyword(s):  
Wind Tunnel ◽  
Noise Reduction ◽  
Porous Materials ◽  
Active Flow Control ◽  
Acoustic Emissions ◽  
Experimental Investigations ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Tunnel Model ◽  
Close Proximity

The introduction of quiet short take-off and landing for civil aircraft operations in close proximity to the population poses important technological challenges. One critical aspect is the realization of extreme lift augmentation at low acoustic emissions. The aircraft concept selected to achieve this goal is a high-lift system equipped with an active flow-control non-slotted flap and a droop nose. For this specific configuration, trailing edge noise becomes a dominant noise source. Porous materials as a passive means for trailing-edge noise reduction are selected and characterized. Results of extensive experimental investigations in the acoustic wind tunnel Braunschweig are presented and discussed to point out the potential and limitations of the selected porous devices. Practical issues related to material manufacturing and integration into the wind tunnel model are addressed. The noise reduction potential of passive porous trailing-edge devices is found to strongly depend on both these aspects. Issues related to the characterization of the porous materials properties are described. Although porous materials are found to be successful at reducing trailing-edge noise emissions, the results indicate that there is still a need for more generic investigations to further clarify the parametric dependencies between noise reduction and material properties.

scholarly journals Theoretical Study of the Acoustic Installation Effects in Closed-Vein Wind Tunnels for the Experimental Characterization of Trailing Edge Noise

2021 ◽  
Vol 11 (20) ◽  
pp. 9718
Author(s):  
Stéphane Redonnet
Keyword(s):  
Wind Tunnel ◽  
A Priori ◽  
Wind Tunnels ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Installation Effects ◽  
Noise Measurements ◽  
Phenomenological Perspective

This study focuses on the acoustic installation effects that may occur during typical aeroacoustic experiments when the latter are conducted in a closed-vein wind tunnel. More precisely, in regard to the specific problem of airfoil trailing edge noise, an analytical model is derived, which allows predicting the wall-induced reverberation effects that such a noise shall be subjected to, when radiating within a closed-vein, hard-wall, wind tunnel. These effects are then assessed through a parametric investigation so as to characterize their impact on in situ acoustic measurements that would be performed using flush-mounted microphones located on the vein’s walls. From a phenomenological perspective, the study highlights how important the reverberation effects by the vein can be. In particular, results reveal how their impact on the noise measurements may greatly vary, depending on the trailing edge noise source location (i.e., the airfoil incidence) and, to a lesser extent, its frequency. The outcomes allow identifying these locations where the installation effects are least, i.e., where to better position a flush-mounted microphone, should in situ noise measurements be conducted. From a methodological viewpoint, the study showcases how the proposed formalism could constitute a simple albeit useful diagnosis tool for mitigating the experimental biases weighing on airfoil trailing edge noise tests to be conducted within closed-vein facilities, whether this would be done a priori by flush-mounting the microphone(s) where these biases are minimal or a posteriori by de-biasing the noise measurements accordingly.

Computation of trailing-edge noise due to turbulent flow over an airfoil

AIAA Journal ◽  
2002 ◽  
Vol 40 ◽  
pp. 2206-2216 ◽  
Author(s):  
A. Oberai ◽  
F. Roknaldin ◽  
T. J. R. Hughes
Keyword(s):  
Turbulent Flow ◽  
Trailing Edge ◽  
Trailing Edge Noise

Noise source location and scaling of subsonic upper-surface blowing

2020 ◽  
Vol 19 (3-5) ◽  
pp. 191-206
Author(s):  
Trae L Jennette ◽  
Krish K Ahuja
Keyword(s):  
Strouhal Number ◽  
Noise Source ◽  
Low Frequency ◽  
Directivity Pattern ◽  
Source Location ◽  
Dipole Source ◽  
Frequency Noise ◽  
Noise Sources ◽  
Trailing Edge ◽  
Trailing Edge Noise

This paper deals with the topic of upper surface blowing noise. Using a model-scale rectangular nozzle of an aspect ratio of 10 and a sharp trailing edge, detailed noise contours were acquired with and without a subsonic jet blowing over a flat surface to determine the noise source location as a function of frequency. Additionally, velocity scaling of the upper surface blowing noise was carried out. It was found that the upper surface blowing increases the noise significantly. This is a result of both the trailing edge noise and turbulence downstream of the trailing edge, referred to as wake noise in the paper. It was found that low-frequency noise with a peak Strouhal number of 0.02 originates from the trailing edge whereas the high-frequency noise with the peak in the vicinity of Strouhal number of 0.2 originates near the nozzle exit. Low frequency (low Strouhal number) follows a velocity scaling corresponding to a dipole source where as the high Strouhal numbers as quadrupole sources. The culmination of these two effects is a cardioid-shaped directivity pattern. On the shielded side, the most dominant noise sources were at the trailing edge and in the near wake. The trailing edge mounting geometry also created anomalous acoustic diffraction indicating that not only is the geometry of the edge itself important, but also all geometry near the trailing edge.

Sign in / Sign up

Export Citation Format

Share Document