Marine propeller noise propagation within bounded domains

Abstract

In the present work, we develop a new methodology to investigate the propagation of acoustic noise originating from a naval propeller, in a bounded marine environment. The propagation in a realistic environment is achieved by coupling the Ffowcs-Williams and Hawkings (FW-H) equation with the acoustic wave equation, overcoming some intrinsic limitations of the FW-H equation. First, the FW-H equation applied to the hydrodynamics field obtained from Large Eddy Simulation, accurately characterizes the propeller source in the acoustic near-field. Then, the propagation in the acoustic far-field is evaluated in an arbitrary domain by solving the acoustic wave equation. After validating the new proposed methodology, we investigate the propagation of the linear part of the noise generated by a naval propeller within a canal. The results show complex interaction between the noise source and the environment: the decay rate of the acoustic energy is strictly related to the distance of the source from the boundaries of the canal; local maxima and minima of the acoustic energy are observed resulting from the superposition of direct and reflected waves; the water–air interface introduces a peculiar asymmetry of the acoustic field associated with the interaction between the acoustic waves.