The problem of translating a frequency domain impedance boundary condition to time domain involves the Fourier transform of the impedance function. This requires extending the definition of the… (More)

This report forms, in two parts, deliverable D2.14 of the TurboNoiseCFD project. It describes the recommended innovative “triple plane pressure” in-duct matching strategy (TPP) at inlet and bypass… (More)

By using a Wiener-Hopf approach, an analytical description is derived of the scattered field of a harmonic sound wave coming out of an open ended annular duct (a semi-infinite cylinder inside of… (More)

For the relatively high frequencies relevant in a turbofan engine duct, the modes of a lined section may be classified in two categories: genuine acoustic 3D duct modes resulting from the finiteness… (More)

Sound transmission through ducts of constant cross section with a uniform inviscid mean flow and a constant acoustic lining (impedance wall) is classically described by a modal expansion, where the… (More)

Asymptotic expansions for small Strouhal number, valid for arbitrary subsonic Mach number, are derived for the solution of a simple problem of the interaction between an acoustic wave, a jet flow and… (More)

Sound transmission through straight circular ducts with a uniform inviscid mean flow and a constant acoustic lining (impedance wall) is classically described by a modal expansion. A natural extension… (More)

In this chapter we give a brief introduction to PDEs. In Section 1.1 some simple problems that arise in real-life phenomena are derived. (A more detailed derivation of such problems will follow in… (More)

An explicit, analytical, multiple-scales solution for modal sound transmission through slowly varying ducts with mean flow and acoustic lining is tested against a numerical finite-element solution… (More)

An explicit Wiener–Hopf solution is derived to describe the scattering of sound at a hard–soft wall impedance transition at x = 0, say, in a circular duct with uniform mean flow of Mach number M . A… (More)