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This paper presents a systematic means of analysing hydrodynamic and hydroacoustic simulations for a marine propeller using an open source multi-physics solver OpenFOAM® (Open Source Field Operation and Manipulation) v1706. OpenFOAM® uses a compressible form of equation of state (EOS) for the working fluid to calculate directly the hydrodynamic source mechanisms and the sound propagation in a compressible liquid domain, simultaneously. Of great importance is the numerical treatment of noise propagation in the presence of complex unstructured meshing and CFD boundaries for inflow/ outflow. Noise damping mechanisms and its effect in absorbing boundary reflections are demonstrated during the study. Appropriate turbulence modelling (e.g. DDES) and 2nd-order accurate schemes in time and space are established which prove sufficient for applications of complex geometries such as propeller, rudder, ship hull etc. A 4-bladed right hand stand-alone marine propeller (D = 0.224 m) rotating at 25 rev/s in the water is simulated. Arbitrary mesh interface (AMI) option in the OpenFOAM® is used between rotating mesh and the static surrounding mesh. Velocity and zero density gradient (patch) is imposed at inlet and a pressure boundary is imposed at the exit. Hub and blades have no-slip wall boundary condition. The cylindrical domain surrounded by an extruded spherical domain are used with propeller located in the centre of the domain. The tip vortex hydrodynamics is visualized along with pressure and density contours. The hydroacoustics propagation of the signal is identified with an impulsive pressure wave. The far-field noise spectra at different azimuthal locations show peaks at blade passing frequency (BPF) and its harmonics along with broadband noise contribution coming from the propeller wake. The spatial spectra further demonstrate the noise source mechanisms at different frequencies. The study analyses noise characteristics of a marine propeller and establishes best practices for the hydroacoustic study of a propeller using OpenFOAM®.
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