Comparison of computational and experimental microphone array results for an 18% scale aircraft model

Abstract

An 18% scale semispan model is used as a platform for examining the efficacy of microphone array processing using synthetic data from numerical simulations. Two hybrid Reynolds-Averaged-Navier-Stokes/Large-Eddy-Simulation (RANS/LES) codes coupled with Ffowcs Williams–Hawkings solvers are used to calculate 97 microphone signals at the locations of an array employed in the NASA Langley Research Center 14 × 22 tunnel. Conventional, DAMAS, and CLEAN-SC array processing is applied in an identical fashion to the experimental and computational results for three different configurations involving deploying and retracting the main landing gear and a part-span flap. Despite the short time records of the numerical signals, the beamform maps are able to isolate the noise sources, and the appearance of the DAMAS synthetic array maps is generally better than those from the experimental data. The experimental CLEAN-SC maps are similar in quality to those from the simulations indicating that CLEAN-SC may have less sensitivity to background noise. The spectrum obtained from DAMAS processing of synthetic array data is nearly identical to the spectrum of the center microphone of the array, indicating that for this problem array processing of synthetic data does not improve spectral comparisons with experiment. However, the beamform maps do provide an additional means of comparison that can reveal differences that cannot be ascertained from spectra alone.