Ducted propeller underwater radiated noise mitigation through leading-edge tubercle modifications

• Main Author: Stark, Callum
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: 2023
• Subjects: Humpback Whale
• Online Access: https://doi.org/10.48730/mzgj-ka22; https://stax.strath.ac.uk/concern/theses/0c483k01k

Anthropogenic underwater radiated noise (URN) has a negative impact on marine life, disrupting key biological functions such as communicating, navigating and catching prey. One of the largest contributors to URN is the various types of marine vessels that occupy the world’s oceans today and of this, the most significant proportion of the noise is emitted from the propulsor. Due to increasing public awareness on this topic, international bodies such as the International Maritime Organization (IMO) published non-mandatory guidelines in2014 to accelerate the reduction in shipping URN. Over the last few decades, there has been growing interest and research around leading-edge (LE) tubercles which are located on humpback whale pectoral fins. They are believed to enhance the manoeuvrability of the marine mammal through prolonged flow attachment and have shown to improve the hydrodynamic and noise performance of marine applications through the introduction of counter-rotatingstreamwise vortex pairs which alter the local flow-field. But, this concept has yet to be applied to ducted propellers and based on the available literature, they could have the capability to address the needs of the shipping industry by reducing the URN signature of marine vessels. Therefore, this research study focuses on the noise mitigation capability of LE tubercles on ducted propellers. Two key areas of noise mitigation were identified through a review of the state-of-the-art literature; LE tubercles applied to the duct to alter the vortex development in the ducted propeller slipstream and therefore, mitigate turbulence and vorticity-induced noise and LE tubercles applied to the blades to influence the sheet cavitation development over the blades and thus, mitigate cavitation-induced noise. This study aims to establish a proof of concept for both identified noise mitigation techniques and understand the core fundamental fluid dynamic mechanisms behind the performance changes using a numerical methodology known as Computational Fluid Dynamics ...