| Searching for ways to change to your engine nozzles that will reduce noise without losing thrust? Studying the trends from one of the NASA Glenn Acoustic Branch’s jet noise prediction codes could let you know if you’re on the right track. The NASA Glenn Acoustics Branch has two programs that have been used to calculate jet noise: JeNo and its predecessor, MGBK.
Development of jet noise prediction codes is multifaceted. Since both JeNo and MGBK predict jet noise using Lilley’s Acoustic Analogy and the mean flow solutions from a Reynolds-Averaged Navier-Stokes (RANS) code, accurate acoustic prediction hinge on accurate aerodynamic predictions. This is why acoustic source modeling, turbulence modeling, together with the development of advanced measurement systems are the leading areas of research in jet noise prediction at NASA Glenn. RANS-based jet noise prediction schemes based on Lilley’s Acoustic Analogy offer relatively quick answers compared to those from alternative methods like Large-Eddy Simulations (LES) or Direct Numerical Simulation (DNS).
The JeNo jet noise prediction code calculates the far-field sound spectral density produced by axisymmetric jets at a user specified observer location and frequency range.
Currently, JeNo has been validated for subsonic and low supersonic, unheated axisymmetric jets. While JeNo offers improvements to the acoustic source modeling and propagation over the methods used in MGBK, MGBK is currently is NASA Glenn’s tool of choice for predicting trends in far field sound pressure levels for complicated 3D geometries.
MGBK has been proven to be useful in analyzing the noise reduction benefits of chevrons—serrations on the edge of turbofan nozzles--which are becoming a familiar sight on today’s commercial airline fleet.
+ Visit our Noise Prediction Software Requests and Documentation
page for more info on JeNo and MGBK
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