Noise radiation from a jet pipe: A benchmark problem for computational aeroacoustics

The aim of this communication is to present an analytical model for the sound radiation from an axisymmetric, semi-infinite duct containing a jet. This model is an idealized description of the noise radiation from aero-engine exhausts and offers a representative benchmark problem against which to assess numerical methods for computational aeroacoustics. The capability to obtain near field solutions is particularly useful in providing reference solutions with which to assess extensively the accuracy of numerical solutions. It should be noted that the problem of sound radiation from a jet pipe includes most of the difficulties that need to be addressed in general applications of computational aeroacoustics to aero-engines, such as the scattering by duct terminations, radiation to the free field, wave refraction at vortex layers and the presence of instability waves. Another interesting feature of the analytical solution is that it is possible to separate explicitly theinstability wave from the rest of the solution. Thus, one can evaluate the possible influence of removing the unstable wave on the acoustic field