Most aeroacoustic noise-prediction methods really on an acoustic analogy featuring a propagation equation associated with source terms. These models were mainly applied to computation of acoustic far fields radiated by simple free flows lie jets. The assumption is made in many formulations that the radiated acoustic field is not perturbed by the shear flow giving rise to the noise sources. These acoustic analogies thus to not provide a full description of acoustic/flow interactions. The Lilley equation was introduced to account, to a certain extent, for mean shear effects on propagation. More recently, this problem has been treated by making use of the linearized Euler equations, which are more flexible and more adequate for numerical simulations. As several types of modes are supported by the Eule equations, problems lined to their coupling have to be considered. It is then necessary to investigate acoustic field computations in complex flows. Our aim in the present article is to validate the wave operator associated with linearized Euler equations. Numerical tests deal with propagation in tow-dimensional sheared ducted flows. Results are compared with other solutions deduced from analytical developments and direct numerical simulations. This study shows that the linearized Euler operator may be used to account for mean effects on wave propagation in the presence of sheared ducted flows. Processes that are specifically considered are 1) convection effects on axial disturbances, 2) refraction effects on oblique wave generation, and 3) source radiation effects on propagation
展开▼
