Acoustic characterization of a multicavity muffler for broadband noise reduction in flow duct applications

Regular paper

Emmanuel Perrey-Debain

Université de Technologie de Compiègne

Wednesday 3 june, 2015, 15:40 - 16:00

0.3 Copenhagen (49)

In this work, acoustic performances of a novel liner concept based on perforated screens backed by air cavities are investigated both numerically and experimentally for circular ducts with mean flow. Dimensions of the cavity are chosen to be of the order or bigger than the wavelength so acoustic waves within the liner can propagate parallel to the duct surface. In this case the liner becomes non-locally reacting and this gives rise to additional resonance effects which renders the attenuation more effective over a broader frequency range. This work emanates from the Cleansky European HEXENOR project which aim is to identify the best multicavity mufflers configuration for reduction of exhaust noise from helicopter turboshaft engines. For the determination of final design parameters which are the perforate plate characteristics and the cavity dimensions, a special boundary integral method is presented. Using a tailored Green’s function for hard wall circular ducts containing uniform mean flow, the numerical technique only requires the discretization of the perforate screen separating the central channel from the air cavities. Comparisons with experimental measurements are shown in the no-flow case. Flow effects on acoustic performances are also analyzed numerically and discussed.

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