Broadband Propeller Noise
Backgrounds
At the 2008 CRS Open Meeting, the CAVDISC Working Group was invited by the Steering Group to develop a research proposal directed towards increasing the understanding of the CRS membership on the subject of broadband cavitation excitation, which resulted in the BROADBAND Working Group. The CAVDISC Working Group was formed to extend the work completed in the earlier PRES and PRES2 Working Groups towards a set of conclusions for the membership to address full-scale ship problems. The basic work program of CAVDISC included, amongst other things, developing an increased understanding of the phenomenological behaviour of full-scale cavitation dynamics to enable the validity of the techniques developed previously, based on model scale behaviour, to be assessed and enhanced.
Objectives
BROADBAND is aimed at increasing our understanding of marine propeller-induced broadband noise and vibration. Typically, the majority of broadband noise is a result of propeller cavitation and is related to either the collapse of cavitation bubbles or the interaction of cavitation vortices. The resulting pressure pulses result in both on-board noise and vibration and far-field radiated noise over a very wide frequency band (from almost DC to in excess of 30 kHz).
Expected Results
The overall objective of the working group is to establish a calculation chain running from broadband noise sources to on-board radiated noise and vibration and far-field radiated noise over a frequency range from DC to 30 kHz. The project will:
- Develop a unified definition of the term ‘broadband excitation over a broad frequency range’.
- Develop a model for broadband excitation.
- Examine the design aspects of propellers focussing on broadband noise.
- Perform model testing to isolate the phenomena.
- Explore the methods necessary to model the response of a ship structure subjected to broadband excitation.
- Evaluate methods for measurement of the ship’s far-field noise signature.