Numerical assessment of education methods for acoustic lines
Project Description: The project aims to validate a numerical model in Lattice-Boltzmann method for impedance deduction of acoustic liners submitted to tangential flow. Validation involves comparing numerical results with experimental data, obtained in the rig of UFSC tests by different methods of eduction for a range of Mach numbers and sound pressure levels.
The move towards a civil aviation market with less socio-environmental impact involves, for example, issues related to energy efficiency and noise control.
One of the main noise control mechanisms used in modern aeronautical engines are the so-called acoustic liners (image 2). Liners are components installed in the nacelle of turbofan engines (image 3), whose main function is noise attenuation in the passing frequency of engine blades. This noise generation mechanism gained prominence as the mainone, as aeronautical engines evolved and began to have high ByPass Ratio ratios.
In this sense, it is of primary importance the appropriate characterization of acoustic liners, which occurs through the determination of their acoustic impedance. It is interesting for the design of these components, however, that this characterization takes into account their actual operating conditions, such as the presence of tangential air flow over its perforated plate, so that the expected mitigation in different scenarios can be determined more atiatenly. In this way, potentially more efficient liners with less impact on the energy efficiency of the engines (drag) can be designed.
The Laboratory of Vibrations and Acoustics of the Federal University of Santa Catarina has a test rig for acoustic liners mounted in anechoic chamber (image 4) able to impose the tangential flow conditions on the liner, and thus induce its impedance under conditions closer to the actual operating.
However, recent studies have shown that the models of impedance deduction of flat walls used to represent the liner result in inconsistencies for the impedance values obtained. The main hypothesis is that such models do not adequately capture the physical interaction between the acoustic field and the turbulent boundary layer (TBL). The physical phenomena involved are of very small scale, and can only be visualized with the aid of numerical models.
Coordinator/ Participants: Prof. Júlio Apolinário Cordioli (coordinator); Prof. Andrey R. da Silva (collaborator/ LVA UFSC); Francesco Avallone (TUDelft); Damiano Casalino (TUDelft); Lucas Meirelles (participant/ LVA UFSC); Lucas Araújo Bonomo (participant/ LVA UFSC); Nicolas Quintino (participant LVA UFSC).
Partners: Delft Technical University (TUDelft); NASA’s Langley Research Center and Fabien Méry of the French Aerospace Laboratory (ONERA); Aeroacoustic Research Consortium (AARC).
Project images:
 Image 1: Turbulent boundary layer on perforated acoustic liner plate. |
 Image 2: Quematic structure of an acoustic liner. |
 Image 3: Acoustic liner in modern turbofan engine. |
 Image 4: Test rig for acoustic liners of LVA-UFSC. |
