A semi-analytical model for installed jet noise is proposed in this paper. The model is composed of two parts corresponding to different sound source mechanisms and takes the ambient flow effect into account. Lighthill's acoustic analogy and a fourth-order space-time correlation model for Lighthill stress tensor are used to model the sound induced by the equivalent quadrupole sources, while the trailing-edge scattering of near-field evanescent jet instability waves are modelled using Amiet's approach. It is found that the trailing-edge scattering of near-field evanescent waves dominates the low frequency amplification of installed jet noise in the far-field when the rigid surface is not close enough to the jet to affect the flow field, while the high-frequency noise enhancement on the reflected side is due to the surface reflection effect. The model agrees well with experimental results at different observer angles apart from deviations caused by mean-flow refraction effect at high frequencies and low observer angles.
展开▼
