Surface temperature measurement of acoustic liners in the presence of grazing flow and thermal gradient

Abstract

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LEONAR liner concept : multiphysics coupling in presence of grazing flow, thermal gradients and high sound levels

“…Near the acoustic resonance, the thermo-acoustic coupling becomes spatially localized; this is mainly linked to the structure and behavior of the sample with respect to high incident SPL, as it appears mostly on the SDOF sample which is less linear than the LEONAR concept regarding SPL effects. The thermo-acoustic coupling observed on these two samples is still smaller than the coupling that appears on SDOF sample with thin facesheets, which are even more nonlinear with respect to incident SPL [18]. The LEONAR sample presents an interest in the context of the UHBR since its acoustic behavior is similar to the equivalent SDOF sample and it takes less space and mass.…”

“…The goal is thus to assess the existence and intensity of the couplings between grazing flow, thermal and acoustic effects for each thermal configuration and each sample. This is achieved by comparing the surface temperatures of the liner with and without acoustic excitation, and using a 1D-approach to link temperature variations to the heat transfer coefficient, following the methodology developed in [18]. The surface temperature is lower on the LEONAR sample than on the SDOF sample in all cases.…”

“…An An assessment of the complete setup's thermal stability was conducted using a plain rigid aluminum sample; this preliminary study is detailed in [18].…”

“…This highlighted strong multiphysics coupling between acoustics, flow and thermal phenomena. Especially, the nonlinear effect due to the SPL on the surface temperature and the thermal exchanges have been highlighted in Lafont et al [18] In this study, a multiphysics assessment will be performed on a LEONAR liner concept and insights will be given on its use in the UHBR context. This concept is compared to an acoustically equivalent SDOF liner.…”

Design and optimization of acoustic liners with a shear grazing flow: OPAL software platform description

“…In the context of aircraft noise reduction in varied applications where a cold or hot shear grazing flow is present (i.e., engine nacelle, combustion chamber, jet pump, landing gear), improved acoustic liner solutions are being sought. These coatings are also subject to operational requirements in terms of aerodynamic impact, mass, thickness, temperature, static and vibration behavior, fire resistance, drainage… (see e.g., [1,2,3]).…”