Turbulence Trailing Edge Noise at Low Mach Number

2005 ◽  
Author(s):  
Sung-Ryong Koh ◽  
Kang-Wook Chang ◽  
Young Moon
Keyword(s):  
Mach Number ◽  
Trailing Edge ◽  
Low Mach Number ◽  
Trailing Edge Noise

Experimental investigation of aerofoil tonal noise at low Mach number

2021 ◽  
Vol 932 ◽  
Author(s):  
Prateek Jaiswal ◽  
Yann Pasco ◽  
Gyuzel Yakhina ◽  
Stéphane Moreau
Keyword(s):  
Experimental Investigation ◽  
Mach Number ◽  
Three Dimensional ◽  
Normal Modes ◽  
Wall Pressure ◽  
Far Field ◽  
Tonal Noise ◽  
Trailing Edge ◽  
Modal Shape ◽  
Low Mach Number

This paper presents an experimental investigation of aerofoil tones emitted by a controlled-diffusion aerofoil at low Mach number ( $0.05$ ), moderate Reynolds number based on the chord length ( $1.4 \times 10^{5}$ ) and moderate incidence ( $5^{\circ }$ angle of attack). Wall-pressure measurements have been performed along the suction side of the aerofoil to reveal the acoustic source mechanisms. In particular, a feedback loop is found to extend from the aerofoil trailing edge to the regions near the leading edge where the flow encounters a mean favourable pressure gradient, and consists of acoustic disturbances travelling upstream. Simultaneous wall-pressure, velocity and far-field acoustic measurements have been performed to identify the boundary-layer instability responsible for tonal noise generation. Causality correlation between far-field acoustic pressure and wall-normal velocity fluctuations has been performed, which reveals the presence of a Kelvin–Helmholtz-type modal shape within the velocity disturbance field. Tomographic particle image velocimetry measurements have been performed to understand the three-dimensional aspects of this flow instability. These measurements confirm the presence of large two-dimensional rollers that undergo three-dimensional breakdown just upstream of the trailing edge. Finally, modal decomposition of the flow has been carried out using proper orthogonal decomposition, which demonstrates that the normal modes are responsible for aerofoil tonal noise. The higher normal modes are found to undergo regular modulations in the spanwise direction. Based on the observed modal shape, an explanation of aerofoil tonal noise amplitude reduction is given, which has been previously reported in modular or serrated trailing-edge aerofoils.

The Simulation of Airframe Noise Applying Euler-Perturbation and Acoustic Analogy Approaches

2005 ◽  
Vol 4 (1-2) ◽  
pp. 69-91 ◽  
Author(s):  
R. Ewert ◽  
J.W. Delfs ◽  
M. Lummer
Keyword(s):  
Mach Number ◽  
Scaling Laws ◽  
Perturbation Approach ◽  
Far Field ◽  
Acoustic Analogy ◽  
Mean Flow ◽  
Trailing Edge ◽  
Airframe Noise ◽  
Trailing Edge Noise ◽  
The Mean

The capability of three different perturbation approaches to tackle airframe noise problems is studied. The three approaches represent different levels of complexity and are applied to trailing edge noise problems. In the Euler-perturbation approach the linearized Euler equations without sources are used as governing acoustic equations. The sound generation and propagation is studied for several trailing edge shapes (blunt, sharp, and round trailing edges) by injecting upstream of the trailing edge test vortices into the mean-flow field. The efficiency to generate noise is determined for the trailing edge shapes by comparing the different generated sound intensities due to an initial standard vortex. Mach number scaling laws are determined varying the mean-flow Mach number. In the second simulation approach an extended acoustic analogy based on acoustic perturbation equations (APEs) is applied to simulate trailing edge noise of a flat plate. The acoustic source terms are computed from a synthetic turbulent velocity model. Furthermore, the far field is computed via additional Kirchhoff extrapolation. In the third approach the sources of the extended acoustic analogy are computed from a Large Eddy Simulation (LES) of the compressible flow problem. The directivities due to a modeled and a LES based source, respectively, compare qualitatively well in the near field. In the far field the asymptotic directivities from the Kirchhoff extrapolation agree very well with the analytical solution of Howe. Furthermore, the sound pressure spectra can be shown to have similar shape and magnitude for the last two approaches.

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.

scholarly journals Low Mach number fluctuating hydrodynamics for electrolytes

2016 ◽  
Vol 1 (7) ◽  
Author(s):  
Jean-Philippe Péraud ◽  
Andy Nonaka ◽  
Anuj Chaudhri ◽  
John B. Bell ◽  
Aleksandar Donev ◽  
...  
Keyword(s):  
Mach Number ◽  
Fluctuating Hydrodynamics ◽  
Low Mach Number

scholarly journals An interface capturing method for liquid-gas flows at low-Mach number

2021 ◽  
Vol 216 ◽  
pp. 104789
Author(s):  
Federico Dalla Barba ◽  
Nicoló Scapin ◽  
Andreas D. Demou ◽  
Marco E. Rosti ◽  
Francesco Picano ◽  
...  
Keyword(s):  
Mach Number ◽  
Gas Flows ◽  
Low Mach Number ◽  
Interface Capturing
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