Acoustic signature of a wetted propeller in the wake of a hydrofoil

Data from Large Eddy Simulations (LES) were exploited to compute the acoustic signature of a wetted propeller working in the wake of a hydrofoil at incidence angles of 0 deg, 10 deg and 20 deg. A computational grid consisting of 1.7 billion points was utilized in the framework of an immersed-boundary (IB) methodology to resolve the fluid dynamics. The Ffowcs-Williams & Hawkings (FWH) acoustic analogy was employed for the computation of the acoustic pressure from the hydrofoil-propeller system in post-processing. The results of the acoustic analysis show that the signature of the propeller is the highest in its upstream and downstream directions, while minima are located on the propeller plane in the direction aligned with the span of the hydrofoil. Also the influence of the incidence angle of the hydrofoil on the acoustic signature of the propeller is analyzed. It is reinforced at large angles, which produce separation phenomena on the suction side of the hydrofoil and enhance the loading component of the sound coming from the propeller blades operating in its wake.