Post-processing methods to extract the acoustic-induced velocity within the orifice of a conventional acoustic liners grazed by a turbulent flow and acoustic wave
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Recent developments in aviation toward ultra-high bypass ratio engines are challenging the application of conventional acoustic liner technology. The less space available for their installation is in contrast with the fact that their size would naturally grow due to the lower rotational speed of the fan. However, in order to develop new liner concepts or meta-liner, we must properly describe the flow-acoustic interaction for conventional and novel liners since this is a key aspect of their acoustic response. To this end, it is essential to decouple the acoustic-induced velocity within the liner orifice from the hydrodynamic one. Several methods have been proposed in the literature to separate the acoustic field from the hydrodynamic one such as spectral proper orthogonal decomposition, triple decomposition, and wavelet, but they have never been adopted for the case of interest where the coupling is strong. In this work, we compare the different methods using as input an existing scale resolved simulation database of a turbulent flow and tonal acoustic excitation grazing a conventional acoustic liner. The impedance obtained by the acoustic field extracted with the different methods will be compared against conventional impedance measurement approaches such as eduction methods and Dean’s method.
