Multi-Domain Approach to CFD Prediction of Underwater Radiated Noise from Marine Propellers

Underwater Radiated Noise (URN) from shipping has increasingly become a topic of concern, as its harmful effects on marine ecosystems become better understood. The shed vorticity in the wake of a marine propeller is broadly responsible for driving sound-generating phenomena across a wide range of operating conditions where cavitation is either present or absent. Accounting for the unsteady pressure in the propeller wake due to the shed vorticity is therefore crucial for simulation of acoustic emissions. The vorticity is itself dependant on both the motion of the propeller and the propeller inflow. The propeller inflow is, in turn, determined by the motion of the vessel and the development of its wake. As a result, prediction of the propeller noise by CFD necessitates prediction of flow features across a wide range of spatial and temporal scales. We present a multi-domain approach to URN prediction that relies on three solutions of increasing fidelity at decreasing physical length scales and discuss the relevant features of each of the corresponding computational domains. At the largest scale, a steady-state Reynolds-averaged simulation of a bare hull is used to establish relevant boundary conditions, while at the smallest scale, a Delayed Detached-Eddy Simulation (DDES) is used to resolve the fluctuating pressure field in the propeller wake. We applied the multi-domain methodology to a model-scale vessel and compared the numerical fluctuating pressure results to experimental measurements.