The technical need in the solicitation calls for “Innovative source identification techniques for airframe noise sources, such as landing gear and high lift systems. This should also include turbulence details related to flow-induced noise typical of separated flow regions, vortices, shear layers, etc.”
In the proposed work, an innovative technique for identifying noise sources and measuring the acoustic spectra and effective source turbulence length scales of noise-creating flows in wind tunnel testing will be developed from TRL 3 to TRL 5. It uses standard microphone phased arrays. The method is especially well suited the weak, extended source with partial coherence, such as trailing edge noise and other airframe noise components. The method has exceptional dynamic range, which should make it possible to measure many sources in wind tunnels that cannot be measured today due to background noise. The method operates effectively looking though a wind tunnel shear layer, which also distinguishes it from other methods at high frequency. Its computation speed is at least one order of magnitude better than competing methods. It is designed to be seamlessly incorporated within larger acquisition and processing systems in use at NASA facilities. It applies well to landing gear and high lift systems.
All three NASA aeronautics research centers will benefit from greatly improved ability to perform measurements of airframe noise and noise of models for Urban Air Mobility vehicles and their components. This may increase the occupancy of several major NASA facilities, including Langley’s 14- by 22-foot wind tunnel. In addition NASA researchers will have a new tool for turbulence measurement.
The method is most suitable for large wind tunnels with open jet and Kevlar-lined jet configurations. There are a number of these at national research centers around the world including in the US, Japan, Europe, and China. They are found at aerospace research centers and automobile manufacturers.