Hydroacoustic Analysis of a Marine Propeller in Open Water Conditions Through LES and Acoustic Analogy

This paper is aimed at studying the hydrodynamic noise generated by a marine propeller in open water conditions. The hydrodynamic field is computed by means of high-fidelity Large Eddy Simulations (LES), coupled with an Immersed-Boundary (IB) approach; these results have been already presented in Posa et al. (2019a), including a complete validation assessment. LES is especially well suited for investigating radiated noise, since all the large energy-carrying structures of the flow are fully resolved with no turbulence modeling. The acoustic field is estimated using the acoustic analogy by suitable formulations of the Ffowcs-Williams and Hawkings (FW-H) equation. In particular, in this paper the analysis is performed using both the porous formulation and the direct formulation of the FW-H equation. For the latter, as a preliminary stage only the linear terms (i.e. those coming from the surface integral over the blade surfaces) are estimated; the analysis of the contribution from the non-linear quadrupole term through the use of volume integrals (i.e. the contribution from the wake of the propeller in the direct formulation) which is mainly responsible for the contribution from the wake is left to future developments.