Several experimental, computational and theoretical results devoted to turbulence jet noise are described. All these results were obtained at CIAM in collaboration with the Boeing Company. The selected topics are combined and described from a single point of view. In spite of the many publications in the classical literature devoted to jet noise, many jet noise problems are not completely solved, and most current jet noise prediction methods are still highly empirical and rely heavily on an existing experimental data base. At the same time, many of the available experimental results are not fully reliable and some are even contradictory. The goal of this paper is, therefore, to explore and discuss some of the possibilities and limitations of classical aeroacoustics methods.

The paper considers the specifics of calculating tonal sound propagating in a flow channel with an installed sound absorbing device. The calculation is performed on the basis of numerical integrating on lin earized nonstationary Euler equations using a code developed by the authors based on the so called discon tinuous Galerkin method. Using the linear theory of small perturbations, the effect of the sound absorbing lining of the channel walls is described with the modified value of acoustic impedance proposed by the authors, for which, under flow channel conditions, the traditional classification of the active and reactive types of lining in terms of the real and imaginary impedance values, respectively, remains valid. To stabilize the computation process, a generalized impedance boundary condition is proposed in which, in addition to the impedance value itself, some additional parameters are introduced characterizing certain fictitious prop erties of inertia and elasticity of the impedance surface.

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