University of California, Irvine
Aeroacoustics Lab

JET-BY-JET DIFFRACTION

Sponsorhip:  NASA Langley Research Center

As part of our comprehensive noise assessment, we are taking a fresh look at the phenomenon of jet-by-jet diffraction, namely how one jet plume scatters sound generated by another.   A theoretical/computational approach has produced results that agree well with experimental measurements done in the 1980s.    The predictions indicate that the jet is a significant scatterer of sound, almost as powerful as replacing the plume with a solid surface. 

The goal is to integrate jet-by-jet diffraction into the next-generation aircraft noise prediction tools developed by NASA.

Publication:

Papamoschou, D. , "Modeling of Jet-by-Jet Diffraction," AIAA-2013-0614 , 51st AIAA Aerospace Sciences Meeting, Grapevine, TX, Jan. 7-10, 2013.  (PDF)

jetjet_bwb.jpg (55564 bytes)

The close proximiy of jet engines in advanced vehicles like the  hybrid-wing-body (HWB), accentuates the phenomenon of jet-by-jet diffraction, which underscores the need to predict its effect on aircraft noise.   

 

jetjet_setup.jpg (37132 bytes)

Modeling considers the jet source as a surface pressure distribution on a cylinder enclosing the jet plume.    Wavepacket models are used to generate this pressure.  This simple model has produced realistic far-field intensities.

jetjet_pattern.jpg (80708 bytes)

An example of how sound emitted from the radiating jet (right) is diffracted by the scattering jet (centered at 0,0).  Regions of attenuation and amplification are evident. 

 

 


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