A study on the hydroacoustic characterisation of a cavitating propeller by dynamic adaptive mesh refinement technique

• Published in: Journal of sound and vibration 2024-07, Vol.582, p.118422, Article 118422
• Main Authors: Köksal, Çağatay Sabri, Aktas, Batuhan, Atlar, Mehmet, Korkut, Emin
• Format: Article
• Language: English
• Subjects: Adaptive mesh refinement; Noise prediction; Tip-vortex cavitation; Underwater radiated noise
• ISSN: 0022-460X; 1095-8568
• DOI: 10.1016/j.jsv.2024.118422

•A mesh refinement technique is utilised to resolve tip-vortex cavitation, essential in predicting the noise.•The proposed technique reduces the computational efforts by adapting both the mesh and the refinement criteria.•The broadband hump in spectra shifts towards the low-frequency as the propeller load increases and hence cavitation. Underwater radiated noise (URN) of a marine propeller has received significant interest in recent decades due to its implications on marine fauna. Therefore, an accurate prediction of URN at an early stage of the propeller design is becoming imperative. This study presents a numerical investigation into the noise prediction of a marine propeller, including cavitation and a comparison with experimental test results obtained from the URN database from the King's College D (KCD) standard propeller series. Amongst the propellers tested in the series, the member KCD-193 was chosen to scrutinise in this study due to the significant variance of the cavitation types experienced by this propeller member and consequent characteristic variations observed in its URN spectral response. Numerical URN predictions of different flow conditions, represented by the advance coefficient and cavitation number, were conducted to investigate their effects on the noise spectrum. These predictions were compared with the experimental results to enable interpretation of the impact of various aspects of the simulation on URN prediction accuracy. In this investigation, one of the most prominent noise sources, tip-vortex cavitation (TVC), was identified as a critical aspect that needs to be captured by the numerical simulations for accurate URN predictions using CFD simulations. The influence of TVC on the spectrum was observed to be significant. The inception and stable presence of TVC dominated the frequency response of the broadband hump. In order to address this, a systematic adaptive mesh refinement strategy was implemented based on the vortex criterion to solve the flow characteristics in the propeller slipstream accurately. To further complement this task, a correlation between the cavitation bubble growth and collapse phenomenon by the sensitivity of the broadband hump on the spectrum was established based on the experimental results. The central frequency of the broadband hump was observed to vary with the advance coefficient and cavitation number. The reduction in the cavitation number resulted in a shift of this hump towards lower frequencies.