Hydroacoustics of an open-water ship propeller*

We use the advective Ffowcs Williams and Hawkings equation to evaluate hydroacoustics of a ship propeller in open sea. The hydrodynamic field is computed using Large Eddy simulation for incompressible flow field; the acoustic field is reconstructed by solving the quadrupole terms through direct calculation of the volume integrals. For the hydrodynamics, we use the dynamic Lagrangian model for the closure of the SGS stresses and a wall-layer model. We consider a propeller well studied in literature for a single value of the advance ratio J=1.068 (https://www.sva-potsdam.de/en/potsdam-propeller-test-case-pptc). A grid of about 6 millions cells is used to reproduce accurately both the stresses over the propeller and the wake, the latter responsible of quadrupole noise. The equations are solved in a fixed-to-the-body frame of reference. Different noise generation mechanisms are investigated separately. Thickness and loading terms related to the propeller shape and velocity, provide significant pressure disturbance in the near field. The quadrupole contribution is investigated in relation to the presence of vorticity persisting in the wake.