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Conference_programme: 27.2 - Underwater Noise II: Sources and remote sensing of the marine environment

Lecture: A velocity-based BEM for modeling generation and propagation of underwater noise from marine propellers

Author(s): Belibassakis Kostas

Main contributors to underwater noise generated from commercial ships are the main engines and auxiliaries (like shaft, reduction gears etc), as well as hydrodynamic interaction of hull flow in calm water and in waves, and finally, the propeller, which usually constitutes the most important source. In this work, a numerical model is developed to study non-cavitating and blade sheet cavitation noise generated from marine propellers operating in unsteady inflow conditions, at the stern of the ship (see, e.g., Kinnas et al 2003). The hydrodynamic part is analyzed by a velocity-based panel method, using vortex elements (Belibasakis & Politis 1998), providing the unsteady pressure on the blades and sheet cavitation data. The latter are subsequently used, in conjunction with Kirchhoff’s formulation concerning radiation from moving surfaces (Farassat, & Myers 1988), to predict the acoustic spectrum at several diameters distance from the propeller, representing the source of marine propeller noise; see also Seol et al (2005). At a first level of approximation, a reduced-order model is used, exploiting information concerning the time history of blade sheet cavity and the unsteady blade forces. Results concerning cavity volume and blade thrust variations are used to calculate the monopole and dipole components of the propeller acoustic spectrum in the low and moderate frequency band. The directivity characteristics the ship propeller are calculated, and its effect on underwater noise propagation is presented comparatively to the omnidirectional source assumption.\n\n\nReferences\nBelibasakis, K.A. Politis, G.K. (1998). A non-linear velocity based Boundary Element Method for the analysis of marine propellers in unsteady flow, International Shipbuilding Progress 45, 93-133.\nFarassat, F., Myers M.K., (1988). Extensions of Kirchhoff’s formula to radiation from moving surfaces, Journal of Sound and Vibration 123, 451–460.\nKinnas S., Lee H.S., Young Y.L. (2003). Modeling of Unsteady Sheet Cavitation on Marine Propeller Blades International Journal of Rotating Machinery Taylor & Francis Inc, 9, 263–277.\nSeol H., Suh J.C., Lee S. (2005). Development of hybrid method for the prediction of underwater propeller noise, Journal of Sound and Vibration 288, 345–360.\n\n\n

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Corresponding author

Name: Prof Kostas Belibassakis

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Country: Greece