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International audience; Ă Duct acoustic network modeling is commonly carried out using the transfer matrix formalism which is limited to the low frequency range as only the plane wave mode is allowed to propagate in the ducts connecting the different elements of the network. The aim of this work is to extend the formalism to higher frequencies by taking into account the multi-mode acoustic propagation. The first step is to compute, via finite element discretisation (FEM), the multi-port scattering matrix of each element. The second step is to rely on simplifying assumptions which are often used for the study of medium-to-high frequency broadband noise. These are: (i) all propagating modes are uncorrelated and (ii) each mode carries the same quantity of acoustic energy. This allows to derive of a multi-port scattering matrix for the acoustic power flow. The method is applied to typical elements such as T-junctions, bends, expansion chambers, lined ducts and contractions. In all cases, the power-flow model is compared to the FEM solution in terms of Transmission Losses. It is concluded that this simplified model is a reliable tool for the analysis of complex networks encountered in HVAC systems. Further work is ongoing by the authors to apply this technique to the simulation of realistic HVAC systems installed in helicopters and this should include the computation of sound generation via appropriate aero-acoustic simulations and the modeling of the acoustic radiation in the cabin.

This paper presents a corrected partitioned scheme for investigating fluid-structure interaction (FSI) that may be encountered by lifting devices immersed in heavy fluid such as liquids. The purpose of this model is to counteract the penalizing impact of the added mass effect on the classical partitioned FSI coupling scheme. This work is based on an added mass corrected version of the classical strongly coupled partitioned scheme presented in [1]. Results show that this corrected version systematically allows convergence to the coupled solution with no dependency on fluid density . The fluid flow model considered here uses a non-stationary potential approach, commonly termed the Panel Method. The advantage of this kind of approach is twofold: first, in restricting itself to a boundary method and, second, in allowing an added mass matrix to be estimated as a post-processing phase.

International audience