SBIR-STTR Award

Aerodynamically-generated noise from aircraft is a critical factor in the continuing development of aviation, as community noise concerns and the associated regulatory requirements constrain the design of new airplanes. In particular, supersonic jets are known to produce broadband and narrow-band (screech tones) noise, which contributes to structural fatigue, in addition to the strong environmental noise pollution. The ability to accurately predict noise mechanisms in gas turbine engines will therefore constitute an essential component of any program aimed at producing aircraft engines with low jet noise emissions. Thaerocomp Technical Corp. (TTC) is proposing to develop a high-fidelity CFD-based software tool for accurate, affordable, and reliable prediction of jet noise at all speeds (subsonic, transonic, supersonic, and hypersonic) under realistic flight conditions. The bottlenecks that currently prevent the availability of such a tool are identified and the innovative research required to remove them are proposed. The proposed tool considerably simplifies the procedure of specifying boundary conditions and suggests a better way to calculate turbulence-generated noise. The new procedure will also identify the best approach to compute the propagation of noise far-field from the point of generation. One of the objectives of the proposed research is to obtain highly accurate noise prediction results for high speed jets. Procedures to establish the feasibility of the Phase I research are proposed

In recent years, jet noise modeling research has primarily followed two different paths: the acoustic analogy approach and Large Eddy Simulation (LES). However, these approaches are, respectively, too restrictive and too expensive for realistic engineering applications. The main objective of the innovative research proposed by Thaerocomp Technical Corporation (TTC) is to develop predictive computational models and a software tool for large-scale turbulence noise in high-speed jets, with fidelity and computational expense suited for engineering applications. This supports a broader objective to develop new concepts for jet noise suppression based on modification and control of large-scale turbulence. The capability of relatively coarse unsteady simulations will be assessed with a focus on the ability to capture, with sufficient accuracy, the relevant features of the large-scale turbulence noise sources controlling the spectral peak at aft angles. The effect of nozzle design modifications on those sources and, hence, noise reduction could then be screened for highly three-dimensional designs such as lobed nozzles. These assessments will be based on comparisons with far field sound, as well as near-field pressure signatures of large-scale turbulence structures, constituting the source sound. Achieving this objective will establish TTC LES methodology as a practical engineering tool addressing peak-frequency, aft-angle noise radiation from large-scale turbulence. This complements the TTC RANS-based methodology for fine-scale turbulence noise developed under Phase I.

Keywords:
Large Scale Noise, Fine Scale Noise, Shock-Assisted Noise, Large Eddy Simulation, Reynolds-Averaged Navier-Stokes Equations (Rans), Wave-Packet Analys