Tubercle Assisted Marine Propulsion Technology

Enhancing hydrodynamic and noise performance of marine propulsors is important to save fuel and to reduce the negative impacts on marine life. Tubercles as applied to both the duct and propeller of a ducted propeller can achieve performance enhancement of ducted propulsors by the alteration of the local flow-field through the introduction of counter-rotating vortex pairs. Our research has been featured into the documentary, Evolve which is produced by the Curiosity Stream discussing nature evolution and its inspiration to human activities.

View the full episode: Link
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Leading-edge tubercle ducted propeller

  • Tubercles introduce streamwise vortex pairs into the propeller inflow
  • Turbulent kinetic energy of the wake flow further downstream is reduced due to the interaction of the vortex pairs with the main ducted propeller vortex structures 
  • ​ Far-field noise can be reduced by 3.4dB OASPL due to the acceleration in the vortex breakdown in the slipstream

Flow separation compartmentalisation and vortex breakdown visualisation 

  • Tubercle amplitude and wavelength will influence hydrodynamic performance of the duct, with a change in amplitude more significant than wavelength. 
  • Optimal tubercle configuration can improve duct thrust in heavy-loaded conditions
  • Optimal tubercle configuration can improve duct thrust by a maximum of 7% by compartmentalising the flow separation on the outside of the duct, which results in efficiency improvement
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Velocity streamlines on outer tubercle and reference duct surfaces

Leading-edge tubercle propeller blades

Tubercles as applied to the propeller can
  • Improve hydrodynamic efficiency by 6.5% in cavitating conditions,
  • Reduce cavitation volume by up to 50% 
  • Reduce far-field noise by 6dB OASPL
  • Reduce the load fluctuation which can improve component life 
This due to the cavitation-funnel effect induced by the counter-rotating vortex pairs.

Sheet cavitation funnel effect visualisation on ducted propeller blades

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Sheet cavitation funnel effect and vortex pair visualisation on open propeller blades

Cavitation and streamwise vortex pair relationship

Featured Research Outcomes: 

Patents: 
WO2022018414A1, WO2022018415A1 and WO2022018416A1
Journal Articles:
1. Stark, C., Shi, W. and Troll, M., 2021. Cavitation funnel effect: Bio-inspired leading-edge tubercle application on ducted marine propeller blades. Applied Ocean Research, 116, p.102864.
2. Stark, C. and Shi, W., 2021. Hydroacoustic and hydrodynamic investigation of bio-inspired leading-edge tubercles on marine-ducted thrusters. Royal Society open science, 8(9), p.210402.
3. Stark, C., Shi, W. and Atlar, M., 2021. A numerical investigation into the influence of bio-inspired leading-edge tubercles on the hydrodynamic performance of a benchmark ducted propeller. Ocean Engineering, 237, p.109593.
Conference Papers:
1. Stark, C. and Shi, W., 2021, June. The influence of leading-edge tubercles on the sheet cavitation development of a benchmark marine propeller. In International Conference on Offshore Mechanics and Arctic Engineering (Vol. 85161, p. V006T06A025). American Society of Mechanical Engineers.
2. Stark, C. and Shi, W., 2021, June. The influence of leading-edge tubercles on the hydrodynamic performance and propeller wake flow development of a ducted propeller. In The 31st International Ocean and Polar Engineering Conference. OnePetro.