Streamwise fences for the reduction of trailing-edge noise in a NACA633018 airfoil

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.

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RANS/CAA Based Prediction of NACA 0012 Broadband Trailing Edge Noise and Experimental Validation

15th AIAA/CEAS Aeroacoustics Conference (30th AIAA Aeroacoustics Conference) ◽

10.2514/6.2009-3269 ◽

2009 ◽

Cited By ~ 25

Author(s):

Roland Ewert ◽

Christina Appel ◽

Jürgen Dierke ◽

Michaela Herr

Keyword(s):

Experimental Validation ◽

Trailing Edge ◽

Trailing Edge Noise ◽

Naca 0012

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Trailing-edge noise reduction of a wing by a surface modification

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-2326 ◽

2021 ◽

Vol 263 (3) ◽

pp. 3194-3201

Author(s):

Varun Bharadwaj Ananthan ◽

R.A.D. Akkermans ◽

Dragan Kozulovic

Keyword(s):

Noise Reduction ◽

Stochastic Approach ◽

Slight Reduction ◽

Noise Sources ◽

Trailing Edge ◽

Sound Sources ◽

Airframe Noise ◽

Trailing Edge Noise ◽

Random Particle ◽

Noise Production

There is an increased emphasis on reducing airframe noise in the last decades. Airframe noise is sound generated by the interaction of a turbulent flow with the aircraft geometry, and significantly contributes to the overall noise production during the landing phase. One examples of airframe noise is the noise generated at a wing's trailing edge, i.e., trailing-edge noise. In this contribution, we numerically explore the local application of riblets for the purpose of trailing-edge noise reduction. Two configurations are studied: i) a clean NACA0012 wing section as a reference, and ii) the same configuration with riblets installed at the wing's aft part. The numerical investigation follows a hybrid computational aeroacoustics approach, where the time-average flow is studied by means of RANS. Noise sources are generated by means of a stochastic approach called Fast Random Particle Mesh method. The results show a deceleration of the flow behind the riblets. Furthermore, the turbulent kinetic energy indicates increased unsteadiness behind the riblets which is shifted away from the wall due to the presence of the riblets. Lastly, the sound sources are investigated by means of the 3D Lamb-vector, which indicates a slight reduction in magnitude near the trailing edge.

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