Multi-port Characterization of a Modal Filter Containing Micro-perforated Panels

© 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Flow duct systems, such as HVAC or Environmental Control Systems, are often an important transmission path for the noise generated by fans, compressors, etc. For the aeroacoustic design of such systems, a compromise has to be made between maximizing the total noise attenuation and optimizing the aerodynamic performance. In this framework, a multi-port formulation can be used to characterize any duct element using an acoustic scatter matrix accounting for a limited number of cut-on modes. In this paper, the multi- port formalism is applied to a set of "modal Filters", consisting of a micro-perforated panel installed along the mid-plane of a duct. These components are designed to attenuate the propagating high-order modes, with a minimal effect on the aerodynamic performance of the system. The inuence of the length of the element, the properties of the panel and the flow through the element have been investigated experimentally, and complemented with time-domain simulations using Runge-Kutta discontinuous Galerkin discretization of the linearized Euler equations and a recursive time-domain transfer admittance formulation.status: publishe