Acoustic characterization of a multicavity muffler for broadband noise reduction in flow duct applications
Regular paper
Université de Technologie de Compiègne
Wednesday 3 june, 2015, 15:40 - 16:00
0.3 Copenhagen (49)
Abstract:
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.