A semi-empirical method is presented that predicts broadband hull-pressure fluctuations and underwater radiated noise due to propeller tip vortex cavitation. The method uses a hump-shaped pattern for the spectrum and predicts the centre frequency and level of this hump. The principal parameter is the vortex cavity size, which is predicted by a combination of a boundary element method and a semi-empirical vortex model. It is shown that such a model is capable of representing the variation of cavity size with cavitation number well. Using a database of model- and full-scale measured hull-pressure data, an empirical formulation for the maximum level and centre frequency has been developed that is a function of, among other parameters, the cavity size. Acceptable results are obtained when comparing predicted and measured hull-pressure and radiated noise spectra for various cases. The comparison also shows differences that require adjustments of parameters that need to be further investigated.

In the present work, a comparison between the results obtained by a panel code with a Reynolds-averaged Navier-Stokes (RANS) code is made to obtain a better insight on the viscous effects of the ducted propeller and on the limitations of the inviscid flow model, especially near bollard pull conditions or low advance ratios, which are important in the design stage. The analysis is carried out for propeller Ka4-70 operating inside duct 19A. From the comparison, several modelling aspects are studied for improvement of the inviscid (potential) flow solution. Finally, the experimental open-water data is compared with the panel method and RANS solutions. A strong influence of the blade wake pitch, especially near the blade tip, on the ducted propeller force predictions is seen. A reduction of the pitch of the gap strip is proposed for improvement of the performance prediction at low advance ratios.

An important input parameter for a recently developed semi-empirical prediction method for the noise generated by cavitating vortices is the diameter of the cavitating vortex. This diameter may be obtained from models of non-cavitating vortices that describe the radial distribution of the azimuthal velocity, for given vortex strength and size of the viscous core. The present paper discusses several vortex models that suit this purpose and compares the distribution of the azimuthal velocity as well as that of the pressure with detailed experimental data for the tip vortex of a rectangular wing obtained from literature.

Cavitating propellers generate pressure fluctuations on the hull of the ship. These pressure fluctuations are usually analyzed in the frequency domain using FFTs and the spectrum is composed of tonals at multiples of the blade passage frequency and a broadband part. The two are often considered separately but a relation between the two exists which has been investigated by theoretical signal analysis. It will be shown that the broadband part is related to the variability of the signal between blade passages and a simple procedure is proposed to quantify the variability in terms of amplitude and phase angle. The procedure has been applied to a data set obtained at sea trials.

Sound maps are essential and practical tools for hindcasting and forecasting sound levels, supporting both environmental assessments and policymaking. The NAVISON (Navis Sonus) project, funded and managed by the European Maritime Safety Agency (EMSA), developed comprehensive shipping sound maps for European seas covering the period from 2016 to 2050. These maps provide results for the 63 Hz and 125 Hz decidecade bands, key frequencies for assessing Good Environmental Status under the EU Marine Strategy Framework Directive. Source levels, computed along Automatic Identification System (AIS) ship tracks using the novel PIANO source model, serve as inputs to a sound mapping tool based on the parabolic equation method, which accounts for environmental factors, such as sound speed profiles, sediment properties, and bathymetry. The NAVISON project delivered hindcast (2016–2023) and forecast (2030, 2040, 2050) sound maps and sound energy densities by vessel type, season, and region. The forecast modeling incorporates scenarios that combine mitigation measures for both greenhouse gas emissions and underwater radiated noise. Maintained and disseminated by EMSA, these outputs provide a comprehensive, long-term perspective on shipping noise trends, quantify vessel-type contributions, enable regional comparisons, and support the evaluation of mitigation strategies.

Sound maps are essential and practical tools for hindcasting and forecasting sound levels, supporting both environmental assessments and policymaking. The NAVISON (Navis Sonus) project, funded and managed by the European Maritime Safety Agency (EMSA), developed comprehensive shipping sound maps for European seas covering the period from 2016 to 2050. These maps provide results for the 63 Hz and 125 Hz decidecade bands, key frequencies for assessing Good Environmental Status under the EU Marine Strategy Framework Directive. Source levels, computed along Automatic Identification System (AIS) ship tracks using the novel PIANO source model, serve as inputs to a sound mapping tool based on the parabolic equation method, which accounts for environmental factors, such as sound speed profiles, sediment properties, and bathymetry. The NAVISON project delivered hindcast (2016–2023) and forecast (2030, 2040, 2050) sound maps and sound energy densities by vessel type, season, and region. The forecast modeling incorporates scenarios that combine mitigation measures for both greenhouse gas emissions and underwater radiated noise. Maintained and disseminated by EMSA, these outputs provide a comprehensive, long-term perspective on shipping noise trends, quantify vessel-type contributions, enable regional comparisons, and support the evaluation of mitigation strategies.