Computational hydroacoustic analysis of the BB2 submarine using the advective Ffowcs Williams and Hawkings equation with Wall-Modeled LES

In the present work we perform the numerical characterization of the hydrodynamic and the hydroacoustic field of a notional submarine geometry (the BB2 submarine). Starting from a model-scale CFD simulation, the full scale acoustic signature of the submarine is derived. We use large eddy simulation with a wall-layer model and perform laboratory-scale numerical experiments at a value of Reynolds number equal to 1.2 x 106. The conditions are those of a wind-tunnel test. The study is carried out focusing on the submarine in its own basic configuration without propeller to highlight the acoustic properties of the hull by itself and to replicate the silent advancing running (where all the non-essential source of noise are shut down and the speed is minimum to minimize the propeller noise). In this configuration, the wake is the main source of noise. The computational hydroacoustic analysis is based on the Ffowcs-Williams and Hawkings equation, here considered in advective form, which is the most suitable form for wind-tunnel-like problems. The results show that the acoustic spectrum is broadband in the far field and the SPL evaluated in the near field contains the signature of coherent structures associated to the presence of the sail and appendages.