Analysis of free-shear flow noise through a decomposition of the Lighthill source term

A decomposition of the Lighthill source term \(\nabla\cdot(\nabla\cdot(\rho \textbf{u}\otimes\textbf{u}))\) is performed with view to more clearly understanding the mechanisms which underlie the production of flow-induced noise. Observation of source fields and associated radiation patterns leads to 3 main observations: (1) the amplitude of subterms in the source field does not scale with the associated acoustic contributions; (2) balances and destructives interferences are present between subterms; (3) source behaviour associated with convection and sound-flow effects is highlighted.