Hydrodynamic noise from a propeller in open sea condition

In the present work a hybrid methodology is used to evaluate the hydrodynamic noise generated by a marine propeller in open sea condition. The hydrodynamic field is computed using Large Eddy simulation under the assumption of incompressible flow field; the acoustic field is reconstructed by applying the advec-tive Ffowcs Williams and Hawkings equation. For the hydrodynamics, we use the dynamic Lagrangian model for the closure of the subgrid-scale stresses and a wall-layer model to skip the resolution of the viscous sub-layer. We consider a propeller well studied in literature for a single value of the advance ratio. A grid of about 6x106 cells is used for reproducing 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. The 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 noise component is obtained by integrating over an external permeable surface. Its contribution is investigated in relation to the presence of vortex persisting in the wake