The Effect of Porous Data Surface Shape and Size on Ship Noise Prediction using the FWH Acoustic Analogy with Incompressible Solver for a Cavitating Propeller

Paper in proceeding, 2022

Using Ffowcs-Williams and Hawkings (FWH) acoustic analogy with an incompressible solver has become a rather common approach for ship noise prediction. Here the method is studied for a model scale container vessel. The numerical study includes both the ship hull and a rotating propeller, using the sliding mesh approach. The simulations are performed for a condition with cavitation around the tip of the propeller blades to study the propeller induced noise including the contribution from cavitation. To complement this study, e.g., to exclude any wall reflections and rotating sources, an additional pure monopole source case study was performed with both incompressible and compressible methodology. Since cavitation is a volume source acoustic term there is a need to use a Porous Data Surface (PDS) in combination with the FWH acoustic analogy. The choice of PDS shape and size using FWH is studied both for the model scale container vessel as well as for the pure monopole source case.
The results show that when using different PDS shapes, a directionality effect is evident when using the incompressible solver. The Sound Pressure Level (SPL) is dependent on the receiver angular location in relation to the PDS. The directionality effect is largest for a PDS shape where there is a large variation in distance from the source to the PDS faces, e.g. box. Furthermore, there is also a receiver distance discrepancy for the incompressible solver with FWH. The SPL curves for different receiver distance do not coincide for higher frequencies. Using a compressible solver and FWH, the shape effect and receiver distance discrepancy is not present.