Using the FW-H equation for hydroacoustics of propellers
Author Lloyd, T.P., Lidtke, A.K., Rijpkema, D.R., Wijngaarden, H.C.J. van, Turnock, S.R. and Humphrey, V.F.
Title Using the FW-H equation for hydroacoustics of propellers
Conference/Journal 18th Numerical Towing Tank Symposium (NuTTS), Cortona, Italy
Month September
Year 2015

Abstract
Marine propeller noise and vibration has been studied in order to reduce acoustic signature, improve fatigue life and comfort onboard, and, more recently, to quantify the impact of maritime noise on the environment. Therefore the importance of acoustic measurements and simulations has increased. Acoustic simulations offer the advantages of avoiding vibration effects on measurement data, as well as the free placement of probes. These are not without difficulty however, and require robust verification, especially in the maritime field, where hydroacoustic computations are relatively uncommon. An attractive approach for making hydroacoustic predictions is an acoustic analogy, such as that of Ffowcs Williams and Hawkings (1969). The processes of sound generation and propagation are then conveniently separated, and acoustic predictions may be made as a post-processing of a hydrodynamic simulation.
In this paper we detail a study into appropriate use of the FW-H acoustic analogy for making hydroacoustic predictions of marine propellers. Two CFD codes (ReFRESCO and OpenFOAM) are used in order to provide additional verification. We focus on issues from the literature resulting from the simulation of a realistic propeller flow, addressing two main questions, namely: how does closure of the PDS in the propeller wake affect the acoustic pressure prediction?; and what is the effect of the axial extent of the PDS in the downstream direction?

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