Isolated Open Rotor Noise Prediction Assessment Using the F31A31 Historical Blade Set

Abstract

In an effort to mitigate next-generation fuel efficiency and environmental impact concerns for aviation, open rotor propulsion systems have received renewed interest. However, maintaining the high propulsive efficiency while simultaneously meeting noise goals has been one of the challenges in making open rotor propulsion a viable option. Improvements in prediction tools and design methodologies have opened the design space for next generation open rotor designs that satisfy these challenging objectives. As such, validation of aerodynamic and acoustic prediction tools has been an important aspect of open rotor research efforts. This paper describes validation efforts of a combined computational fluid dynamics and Ffowcs Williams and Hawkings equation methodology for open rotor aeroacoustic modeling. Performance and acoustic predictions were made for a benchmark open rotor blade set and compared with measurements over a range of rotor speeds and observer angles. Overall, the results indicate that the computational approach is acceptable for assessing low-noise open rotor designs. Additionally, this approach may be used to provide realistic incident source fields for acoustic shielding/scattering studies on various aircraft configurations.

Structured Overlapping Grid Simulations of Contra-Rotating Open Rotor Noise

“…In addition, the low-speed configuration is also being analyzed using two additional NASA developed CFD codes OVERFLOW and FUN3D. 18 The compressible hybrid RANS/LES equations are solved using a finite-di↵erence formulation applied to the curvilinear transformed system of equations in strong conservation law form. 19 The Spalart-Allmaras (SA) 20 turbulence model is used as the base RANS closure model, and a modified version of the Detached Eddy Simulation (DES) model 21,22 (modifications described in III.B) is used to transition from RANS to LES with a Smagorinsky-like sub-grid scale model in the LES regions.…”

A Review of Distributed Electric Propulsion Concepts for Air Vehicle Technology

“…This high-lift augmentation enabled the aircraft to take off and land on short runways with steeper departure and approach angles, which further reduced community noise. For the NASA X-57 flight demonstrator, several papers were presented on the acoustic aspect of the distributed propeller system that are mounted at the leading edge of the wing [65][66][67]. In particular, Nark and his colleagues used multiple computational fluid dynamics codes to assess the aerodynamic performance of the configuration and then used the results to predict the isolated high-lift propeller noise source [66].…”

Aerodynamic Performance and Acoustic Measurements of a High-Lift Propeller in an Isolated Configuration

“…This collective setting was originally implemented in Ref. 19 for the purpose of better matching of predicted thrust values between PAS and CFD results for a simulated takeoff condition (case 3 in Table 2). To obtain an initial estimate of the effects of blade-to-blade variation, PAS is used to superimpose the cases of individual blade passages for a set of geometrically modified blade shapes.…”