Aeroacoustic testing on a full aircraft model at high Reynolds numbers in the European Transonic Windtunnel

TL;DR

This study demonstrates an approach for aeroacoustic testing of a full aircraft model at high Reynolds numbers in a wind tunnel, revealing how Reynolds and Mach numbers influence noise sources and their characteristics.

Contribution

It introduces a comprehensive methodology for assessing aeroacoustic emissions at near-real Reynolds numbers, including measurement setup, flow parameter selection, and analysis techniques.

Findings

Reynolds number has a non-linear impact on aeroacoustic emissions.

Slotted test sections have minimal influence on beamforming results.

Sources exhibit non-linear Mach number dependency but are self-similar across a range.

Abstract

This paper presents an end-to-end approach for the assessment of pressurized and cryogenic wind tunnel measurements of an EMBRAER scaled full model close to real-world Reynolds numbers. The choice of microphones, measurement parameters, the design of the array, and the selection of flow parameters are discussed. Different wind tunnel conditions are proposed which allow separating the influence of the Reynolds number from the Mach number, as well as the influence of slotted and closed test sections. The paper provides three-dimensional beamforming results with CLEAN-SC deconvolution, the selection of regions of interest, and the corresponding source spectra. The results suggest that slotted test sections have little influence on the beamforming results compared to closed test sections and that the Reynolds number has a profound, non-linear impact on the aeroacoustic emission that lessens with increasing Reynolds number. Further, sources show a non-linear Mach number dependency at constant Reynolds number but are self-similar in the observed Mach number range. The findings suggest that it is possible to study real-world phenomena on small-scale full models at real-world Reynolds numbers, which enable further investigations in the future such as the directivity of sources.