Numerical prediction of the noise radiated from silent non cavitating marine propellers

Assessment and improvement of the radiated acoustic footprint within the design stage of ships has always been crucial to Naval Group, especially at high speed where main noise sources are hydrodynamic flow and propeller. To evaluate and optimize the propeller radiated noise, Naval Group relies mainly on high level propeller experiments in the Large Hydrodynamic Tunnel (GTH), a very specific facility of DGA Hydrodynamics. But with shorter delays required for shipbuilding, it is also necessary to invest in numerical approaches to estimate the propeller main contributions to noise and to reduce the number of model tests, which remains a technical challenge in this domain. These numerical approaches are also complementary to model tests in their capability to provide additional information like the seabed effect or the propeller radiated noise directivity, which are not available in the tunnel experiments. Each developed numerical approach must be evaluated by comparisons to experimental data or through numerical benchmarks. One of the biggest difficulties in the application of these approaches is the adaptation of models widely used and validated for aeronautical applications but not necessarily in sea conditions. The challenge is then to develop and adapt models for marine applications where predominant contributions may be different because of a much lower Mach number and a strong coupling between a heavy fluid and the structure.