The signature of a propeller–rudder system: Acoustic analogy based on LES data. (1st September 2022)

• Record Type: Journal Article
• Authors: Posa, Antonio; Felli, Mario; Broglia, Riccardo
• Is Part Of: Ocean engineering. Volume 259(2022)
• Publication Date: 2022-09-01
• Subjects: Large-Eddy Simulation -- Acoustic analogy -- Ffowcs-Williams and Hawkings equation -- Propeller–rudder interaction -- Immersed boundary method; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2022.112059
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: The acoustic analogy is utilized to analyze the sound from a propeller–rudder system, exploiting data from high-fidelity Large-Eddy Simulations, performed on a cylindrical grid consisting of 3.8 billion points. Simulations were conducted with the downstream hydrofoil at incidence angles of 0 °, 5 °, 10 ° and 15 ° . The analysis demonstrates the significant effect of the downstream hydrofoil in increasing the sound pressure levels, especially due to the loading noise from its surface, but also as a result of the enhanced complexity of the wake topology. For increasing angles of incidence, the wake experiences a growing elongation in the direction of the span of the hydrofoil and higher values of cross-stream velocity, reinforcing the shear between the wakes shed by the propeller and the hydrofoil, respectively. A very complex directivity of the acoustic signature develops, whose dependence on the orientation of the hydrofoil is variable across both the azimuthal and the streamwise directions. Separation on the suction side of the hydrofoil for large incidence angles has the effect of reducing the loading component of noise from its surface, which is the leading one, with the exception of the radial coordinates within a few diameters from the axis of the propeller and its wake. Highlights: Higher sound levels in comparison with the open-water propeller. Pressure fluctuations on the hydrofoil dominating the sound from the system. Sound levels weakly affected by the orientation of the hydrofoil. Growing elongation of the acoustic signature across the span for larger incidences. Separation at large incidence angles of the hydrofoil reducing the loading noise.