NASA Glenn Research Center Develop Software to Predict Aircraft Engine Noise

Based on reporting by NASA News Releases:

Research teams at NASA’s Glenn Research Center are engaged in developing both the theory and the software necessary to predict noise generated by aircraft engines, which assists engineers in designing and analyzing improved aircraft propulsion systems. Copies of this software are available for request from NASA’s Software Catalog.

JeNo is a jet noise prediction code that utilizes Lilley’s Acoustic Analogy and mean flow solutions derived from a Reynolds-Averaged Navier-Stokes (RANS) code to calculate the far-field sound spectral density produced by axisymmetric jets at a specified observer location and frequency range. JeNo has been validated for unheated axisymmetric jets operating in both subsonic and low supersonic regimes. Copies of the JeNo code can be obtained from NASA’s Software Catalog.

MGBK was developed prior to JeNo, and researchers at NASA GRC have utilized MGBK to forecast trends in jet noise for complex aircraft engine exhaust nozzles. MGBK was employed to examine the noise reduction advantages provided by chevrons—serrations located on the edge of turbofan nozzles, which are common on many contemporary commercial aircraft engines. Copies of the MGBK codes can be requested from NASA’s Software Catalog.

V072 has proven useful in the study of rotor/stator interaction tone noise, relying on simplistic models of fan flow and geometry. For designing a low-noise fan stage, V072 can aid in making informed decisions regarding design parameters such as blade and vane counts, rotor-stator spacing, and stator vane sweep and lean. V072 may be a suitable tool for obtaining rapid noise estimates during the early design phase. Copies of V072 can be requested from NASA’s Software Catalog.

TFaNS allows for the prediction of tone noise resulting from rotor/stator interaction; furthermore, it can account for blade row acoustic coupling effects, including transmission and reflection, and propagate these tones to the far field. Similar to V072, TFaNS operates quickly and can be used in early design stages for trend analysis. Copies of TFaNS can be requested from NASA’s Software Catalog.

When simpler models are insufficient, Linflux enables the study of realistic, three-dimensional flows and blade geometries. Linflux predicts rotor/stator tone noise, and like all software developed by the NASA Glenn Acoustics Branch, it has undergone rigorous validation against experimental data. Linflux requires more computational resources compared to V072 and TFaNS because it models a greater extent of the physics involved. Copies of Linflux can be requested from NASA’s Software Catalog.

BFANS can be used to calculate the broadband noise generated when turbulence impinges upon the leading edges of rotor blades and stator vanes, using estimates of turbulence intensity and characteristic length scale as input. Calculations performed with BFANS, when combined with experimental data from tests conducted at facilities such as NASA Glenn’s 9’x 15’ Low Speed Wind Tunnel, can help identify the noisiest elements within a fan stage. Copies of BFANS can be requested from NASA’s Software Catalog.

RSI is a computer code designed to calculate the spectrum of broadband noise that results from the interaction between fan rotor wake turbulence and the fan exit guide vanes. The software computes the spectra of acoustic power both upstream and downstream of the stator on a mode-by-mode basis at every frequency of interest, provided information about the incident turbulence characteristics is given. The target frequencies are arbitrary and do not need to be harmonics of the fan's blade passing frequency. Copies of RSI can be requested from NASA’s Software Catalog.

WOBBLE code computes the tone noise associated with propellers that experience varying inflow angles and predicts the axial and circumferential directivity. The inflow angle is specified using the aircraft's yaw, pitch, and roll angles. The acoustic model employed is exact and accounts for all unsteady sources, such as thickness and loading effects from the blades. Copies of WOBBLE can be requested from NASA’s Software Catalog.

MPT code enables engineers to estimate multiple pure tone noise, also known as “buzz saw” noise, which arises from rotor locked shocks when the fan blade tip speed is supersonic. The MPT codes also incorporate flow predictions from a Computational Fluid Dynamics (CFD) code as input. This tool allows engineers to study the actual effects of blade-to-blade differences caused either during fabrication (manufacturing variations) or during hot-running operation (blade setting angle and untwist variations). Copies of the MPT code can be requested from NASA’s Software Catalog.

ADPAC, which was developed by the Allison Engine Company under contracts with the Glenn Research Center, solves tightly coupled internal and external flows within future-concept short-duct turbofan engines. ADPAC is described as one of their flexible validated CFD tools. The characteristics of problems that can be modeled with ADPAC include 2D/axisymmetric/3D/mixed, steady/unsteady, inviscid/viscous, rotating/non-rotating/mixed components, and scenarios involving bleeds, leakages, and injection. ADPAC was specifically developed for the aerodynamic analysis of propulsion systems. Copies of the ADPAC code can be requested from NASA’s Software Catalog.