Impact of the Green function in acoustic analogies for flow noise predictions at low Mach number

It is known that hydrodynamic noise can be a major contribution to the total sound radiated by a ship. It is in part attributed to the interaction between turbulent eddies with appendages and marine propeller blades. Because hydrodynamics is associated with very low Mach numbers, direct noise computation methods are too expensive. Other approaches must be chosen, based on acoustic analogies which consist first in modeling the incompressible turbulent flow and then in computing the noise radiated by this flow. We focus on Lighthill's wave equation, solved using the free space Green function or a tailored Green's function in presence of an arbitrary geometry. Unlike many studies from the literature where the impact of the chosen turbulent model is evaluated over a semi-infinite plate, the objective of this study is to evaluate the impact of the chosen Green function on the predicted broadband flow noise for a fixed semi-empirical turbulence model. The impact of the chosen tailored Green function on the radiated noise spectra and directivity diagrams is evaluated considering various analytical and numerical tailored Green's functions.