| Finding ways to confine objectionable noise from aircraft to the airport boundary means that we need to understand both tone and broadband noise. Several codes have been developed to study how fan broadband noise is generated, and how it propagates away from the engine. Since sound can be directional, estimates of the directivity pattern may aid engineers to apply treatment at the right spot when generation of the noise can’t be avoided. Currently, the NASA Glenn Acoustics Branch can provide fan broadband noise analysis from the following codes:
BFANS:
Using estimates of turbulence intensity and characteristic length scale as input, BFANS can be used to calculate the broadband noise generated by turbulence impinging on the leading edges of the rotor blades and stator vanes. Calculations with BFANS, combined with experimental data from tests at facilities like NASA Glenn’s 9’x 15’ Low Speed Wind Tunnel, can be used to hunt down the noisiest components in a fan stage.
+ Visit our Noise Prediction Software Requests and Documentation
page for more info on BFANS
FanBB:
Applied to a carefully chosen model problem, the FanBB code can provide a wealth of insight into fan broadband generation. Based on studies demonstrating the importance of quadrupole noise, the FanBB code includes a quadrupole noise model for fan broadband noise prediction. FanBB incorporates 3D effects in the noise model, a simplified procedure for predicting directivity, and an anisotropic turbulence model, and has been validated against experimental data for a number of fans.
+ Visit our Noise Prediction Software Requests and Documentation
page for more info on the FanBB codes
Broadband Directivity:
A fan produces broadband sound over a wide range of frequencies, and over a wide range of propagating modes at each frequency. To calculate the fan broadband radiation patterns using conventional modal methods continues to be computationally intensive and time consuming. The approximate methods of this Broadband Directivity code enable users to get an estimate much more quickly.
+ Visit our Noise Prediction Software Requests and Documentation
page for more info on this Broadband Directivity code
RSI
RSI is a FORTRAN computer code for calculating the spectrum of braodband noise produced as a result of the interaction of the fan rotor wake turbulence with the fan exit guide vanes. The code computes the spectra of acoustic power upstream and downstream of the stator on a mode-by-mode basis at each frequency of interest given information about the incident turbulence characteristics. The target frequencies are arbitary and need not be harmonics of the blade passing frequency of the fan.
+ Visit our Noise Prediction Software Requests and Documentation page for more info on this RSI code
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