High Frequency Jet Noise Installation Effects for an Under Wing Mounted Aircraft

2008 ◽  
Author(s):  
Philip Mc Laughlin ◽  
Rod Self ◽  
Christopher Powles ◽  
Christopher Wrighton ◽  
Paul Strange ◽  
...  
Keyword(s):  
High Frequency ◽  
Jet Noise ◽  
Installation Effects

Turbulence Modelling and Meshing Developments for the Prediction of Jet Noise Installation Effects

2016 ◽  
Author(s):  
Charles R. Mockett ◽  
Marian Fuchs ◽  
Felix Kramer ◽  
Ulf Michel ◽  
Mathias Steger ◽  
...  
Keyword(s):  
Jet Noise ◽  
Turbulence Modelling ◽  
Installation Effects

Predictive LES for Jet Aeroacoustics: Current Approach and Industrial Application

2016 ◽  
Author(s):  
James Tyacke ◽  
Iftekhar Naqavi ◽  
Zhong-Nan Wang ◽  
Paul Tucker ◽  
Peer Boehning
Keyword(s):  
Numerical Methods ◽  
Jet Noise ◽  
Reynolds Numbers ◽  
Current Approach ◽  
Navier Stokes ◽  
Jet Flows ◽  
Installation Effects ◽  
Eddy Simulation ◽  
The Cost ◽  
Near Future

The major techniques for measuring jet noise have significant drawbacks, especially when including engine installation effects such as jet-flap interaction noise. Numerical methods including low order correlations and Reynolds-Averaged Navier-Stokes (RANS) are known to be deficient for complex configurations and even simple jet flows. Using high fidelity numerical methods such as Large Eddy Simulation (LES) allow conditions to be carefully controlled and quantified. LES methods are more practical and affordable than experimental campaigns. The potential to use LES methods to predict noise, identify noise risks and thus modify designs before an engine or aircraft is built is a possibility in the near future. This is particularly true for applications at lower Reynolds numbers such as jet noise of business jets and jet-flap interaction noise for under-wing engine installations. Hence, we introduce our current approaches to predicting jet noise reliably and contrast the cost of RANS-Numerical-LES (RANS-NLES) with traditional methods. Our own predictions and existing literature are used to provide a current guide, encompassing numerical aspects, meshing and acoustics processing. Other approaches are also briefly considered. We also tackle the crucial issues of how codes can be validated and verified for acoustics and how LES based methods can be introduced into industry. We consider that hybrid RANS-(N)LES is now of use to industry and contrast costs, indicating the clear advantages of eddy resolving methods.

scholarly journals Jet noise shielding provided by a hybrid wing body aircraft

2018 ◽  
Vol 17 (1-2) ◽  
pp. 135-158 ◽  
Author(s):  
Michael J Doty ◽  
Thomas F Brooks ◽  
Casey L Burley ◽  
Christopher J Bahr ◽  
Dennis S Pope
Keyword(s):  
High Frequency ◽  
Jet Noise ◽  
Low Noise ◽  
Shielding Effectiveness ◽  
Axisymmetric Nozzle ◽  
Jet Engine ◽  
Stage 4 ◽  
Noise Shielding ◽  
Noise Measurements ◽  
Chevron Nozzle

One approach toward achieving NASA's aggressive N+2 noise goal of 42 EPNdB cumulative margin below Stage 4 is through the use of novel vehicle configurations like the hybrid wing body. Jet noise measurements from a hybrid wing body acoustic test in the NASA Langley 14- by 22-Foot Subsonic Tunnel are described. Two dual-stream, heated Compact Jet Engine Simulator units are mounted underneath the inverted hybrid wing body model on a traversable support to permit measurement of varying levels of shielding provided by the fuselage. Both an axisymmetric and low noise chevron nozzle set are investigated in the context of shielding. The unshielded chevron nozzle set shows 1–2 dB of source noise reduction (relative to the unshielded axisymmetric nozzle set) with some penalties at higher frequencies. Shielding of the axisymmetric nozzles shows up to 6.5 dB of reduction at high frequency. The combination of shielding and low noise chevrons shows benefits beyond the expected additive benefits of the two, up to 10 dB, due to the effective migration of the jet source peak noise location upstream for increased shielding effectiveness. Jet noise source maps from phased array results processed with the deconvolution approach for the mapping of acoustic sources algorithm reinforce these observations.

scholarly journals An experimental study of the effects of lobed nozzles on installed jet noise

2019 ◽  
Vol 60 (12) ◽  
Author(s):  
Benshuai Lyu ◽  
Ann P. Dowling
Keyword(s):  
Noise Reduction ◽  
High Frequency ◽  
Jet Noise ◽  
Intermediate Frequency ◽  
Dominant Mode ◽  
Frequency Noise ◽  
Mean Flow ◽  
Instability Waves ◽  
Jet Mixing ◽  
Jet Instability

Abstract Jet noise remains a significant aircraft noise contributor, and for modern high-bypass-ratio aero-engines the strong interaction between the jet and aircraft wing leads to intensified installed jet noise. An experiment is carried out in this paper to study the effects of lobed nozzles on installed jet noise. It is found that the lobed nozzles, compared to round nozzles, have similar effects on installed jet noise for all the plate positions and Mach numbers tested. On the shielded side of the plate, the use of lobed nozzles leads to a noise reduction in the intermediate- and high-frequency regimes, which is thought to be due to a combination of enhanced jet mixing and more effective shielding effects by the flat plate. On the reflected side of the plate, noise reduction is only achieved in the intermediate frequency range; the little noise reduction or a slight noise increase observed in the high-frequency regime is likely due to enhanced jet mixing. On both sides of the plates, little noise reduction is achieved for the low-frequency noise due to the scattering of jet instability waves. This is likely to be caused by the fact that lobed nozzles cause negligible change to the dominant mode 0 (axisymmetric) jet instability waves. That the jet mean flow quickly becomes axisymmetric downstream of the jet exit could also play a role. Graphic abstract

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