Session: 06-15-01 Unsteady Hydrodynamics, Vibrations, Acoustics and Propulsion

Paper Number: 78157

78157 - Marine Ducted Thruster Underwater Radiated Noise Control Through Leading-Edge Tubercle Blade Modifications - a Numerical Hybrid Approach 

Underwater radiated noise (URN) has become a critical early design factor for marine propulsors for all types of marine vessel due to the increased public awareness of the negative impact it has on marine life.  Due to this, international bodies such as the international maritime organization (IMO) published non-mandatory guidelines to encourage the reduction in anthropogenic URN from the shipping industry. To address this issue, noise mitigation devices must be designed, developed, and tested.

Ironically, a marine mammal impacted by the negative by-products of the shipping industry is the inspiration behind this research. The humpback whale has small bumps located on the leading-edge of the pectoral fin known as leading-edge (LE) tubercles that aid in its ability to perform acrobatic manoeuvres to catch prey. LE tubercles have shown evidence through numerical and experimental investigations of providing hydrodynamic and hydroacoustic performance enhancements for a range of devices such as hydrofoils, rudders and tidal turbines in cavitating conditions.

This paper aims to assess the noise mitigation capability of LE tubercles on a benchmark Kaplan-type ducted propeller blade in cavitating conditions using computational fluid dynamics (CFD), where improved delayed detached eddy simulations (IDDES) are implemented to solve the hydrodynamic flow-field and the Schnerr-Sauer model is used to describe the cavitation behaviour. Both near and far-field noise is predicted within the hydroacoustic analysis. The Ffowcs-Williams Hawkings (FW-H) acoustic analogy is utilised to propagate the generated noise into the far-field where linear and non-linear source contributions are all considered by employing a porous FW-H approach.

In summary, it was found that the LE tubercle modified ducted propeller blades could produce a noise reduction in the far-field at most test conditions considered to a maximum of 6dB OASPL while simultaneously improving hydrodynamic performance in terms of total thrust and propulsive efficiency in cavitating conditions. This is believed to be predominantly due to the ability of the tubercle modification to reduce the sheet cavitation severity across the blades.

Presenting Author: Callum Stark University of Strathclyde

Authors:

Callum Stark University of Strathclyde
Weichao Shi University of Strathclyde
Yunxin Xu University of Strathclyde
Moritz Troll University of Strathclyde