Full-scale cabin noise from turbulent boundary layer excitation, Part 1: Wall-pressure measurement and analysis
Résumé
The present paper is part of a two-fold study focused on cabin noise conducted within the frame of the Canoble project of the EU's CleanSky2 programme. The turbulent boundary layer developing on the fuselage creates excitation through wall pressure fluctuations that are, to some extent, transmitted and radiated inside the cabin, contributing to a significant part of the noise during cruise. Many studies have looked into the properties and structures of wall pressure fluctuations beneath a turbulent boundary layer, however there is still a lack of knowledge for some of their components and on the effect of pressure gradients, more so on realistic geometries. Hot-wires and hot-films have been used to characterise the boundary layer while newly developed antennas of digital MEMS microphones served for the measurement of wall pressure. The latter technology had previously been tested in duct flow by some of the authors and was able to isolate acoustic components from the hydrodynamic ones. The microphones themselves are embedded into a circuit board which reduces the overall thickness to only a few millimetres, and enables the measurements to be carried out without intrusive modification of the fuselage. Such an approach opens the door to in-flight tests in the future. These measurements have been performed on a scale-one mock-up of the fore part of a Dassault Aviation business jet, in an industrial-size wind tunnel. The boundary layer parameters along with the wall pressure spectra that were successfully measured will serve as inputs for the second part focusing on vibrational behaviour and noise radiation inside the cabin © Proceedings of the 26th International Congress on Sound and Vibration, ICSV 2019. All rights reserved.