Some Experiments on the Transmission of Propeller Cavitation Noise into the Ship’s Structure

Summary

Exploratory analysis of the sound paths that lead from the propeller cavitation region into the ship’s hull by means of measurements in scale models and on full scale (8–400 Hz) of the source volume-velocity U (m³/s), response pressure p(Pa) in front of shell plates and hull vibratory velocity v(m/s). Hull surface impedance p/v shows minima interpreted as corresponding to (plate etc.) series resonances, and hull pressure ratio p/p(incident) maxima to shunt resonances. Transfer function U/v appears not explained by known plane wave theory, though p/v is satisfactorily. Experiments indicate that more than 10 dB better cavitation noise isolation may result from increased hull stiffness, e.g. by halving the frame spacing; moreover serious resonance risk if pressure-release coating would have insufficient compliance. Recommendation to measure propellers’ U and aft-end structures’ U/v and to adapt propeller blade rate to U/v maxima.

The erratum of this chapter is available at http://dx.doi.org/10.1007/978-94-009-3515-0_59