Modelling the noise emitted by turbulent jets is made difficult by their acoustic inefficiency:
only a tiny fraction of the near-field turbulent kinetic energy is propagated to the far field as
acoustic waves. As a result, jet-noise models must accurately capture this small, acoustically
efficient component hidden among comparatively inefficient fluctuations. In this paper, we
identify this acoustically efficient near-field source from large-eddy simulation data and use it
to inform a predictive model. Our approach uses the resolvent framework, in which the …

We present an analysis aiming to identify the acoustically efficient forcing components in
subsonic jets using an LES database. The forcing terms, which correspond to the source
terms in the classical terminology of acoustic analogies, are defined within the resolvent
framework. We extract from a jet database at Mach number, M= 0.4, which contains both
state and forcing data, a low-rank representation of the acoustic field and a low-rank forcing
that is correlated with it. We show that the forcing components that generate 99% of the …