Recently the leading-edge tubercles on the pectoral fins of humpback whales have attracted the attention of researchers who wish to exploit this feature in the design of turbine blades to improve the blade performance. The main objective of this paper is therefore to make a further investigation into this biomimetic design inspiration through a fundamental research study involving a hydrofoil section, which represents a straightened tidal turbine blade, with and without the leading-edge tubercles, using computational and experimental methods. Firstly a computational study was conducted to optimise the design of the leading-edge tubercles by using commercial CFD code, ANSYS-CFX. Based on this study the optimum tubercle configuration for a tidal turbine blade with S814 foil cross-section was obtained and investigated further. A 3D hydrofoil model, which represented a "straightened" tidal turbine blade, was manufactured and tested in the Emerson Cavitation Tunnel of Newcastle University to investigate the effect of various tubercle options on the lift and drag characteristics of the hydrofoil. The experiments involved taking force measurements using a 3-component balance device and flow visualisation using a Particle Image Velocimetry (PIV) system. These tests revealed that the leading-edge tubercles may have significant benefits on the hydrodynamic performance of the hydrofoil in terms of an improved lift-to-drag ratio performance as well as reducing the tip vortex which is main cause of the undesirable end-effect of 3D foils. The study explores further potential benefits of the application of leading-edge tubercles on tidal turbine blades

This paper focuses on the study of cavitation and underwater noise performance of a biomimetically improved horizontal axis tidal turbine (HATT) with a leading edge design inspired by the tubercles on the pectoral fins of humpback whales. Systematic model tests were recently conducted and details of this test campaign together with the findings are summarised in the paper. Several full-scale tidal turbine application cases were studied to understand the full-scale operating conditions considering the characteristics of varied kinds of tidal energy devices, the varying wave height and the flood/ebb tide. A systematic test regime was then designed and conducted. A set of tidal turbines with different leading-edge profiles was manufactured and tested under different loading and hence cavitation conditions. During the tests, cavitation was observed and underwater noise level was measured in comparison with the cavitation and noise performance of a counterpart HATT without tubercles. The tested turbines displayed two main types of cavitation patterns independent of the tubercles. These were steady tip vortex cavitation and relatively intermittent cloud cavitation with a misty appearance. The leading-edge tubercles triggered the cavitation onset earlier for the tidal turbine but constrained the cavitation region to the trough between tubercles with a lesser extent on the blades. The noise performance was strongly related to the blade cavitation hence it was influenced by the leading-edge tubercles. While the turbine was working under the non-cavitating conditions the total noise level was similar to the background noise level. With the increase of the tip speed ratio the noise level was increased, while increasing blade pitch angle reduced the noise level due to lower blade loading. Cavitation inception and noise diagrams are provided as a database for future studies

This paper contributes to the investigations into the feasibility of improving the performance of a marine current turbine using a biomimetic concept inspired from the leading-edge tubercles on the flippers of humpback whales. An experimental test campaign was recently conducted in the Emerson Cavitation Tunnel at Newcastle University and details of this test campaign together with the findings are summarised in the paper A set of tidal turbines with different leading-edge profiles was manufactured and tested to evaluate the hydrodynamic performance. Various tests were conducted at different flow speed and different pitch angle settings of the turbine blades. The results showed that the models with the leading-edge tubercles had higher power coefficients at lower tip speed ratios (TSRs) and at lower pitch angle settings where the turbine blades were working under stall conditions. Therefore, the tubercles can reduce the turbines' cut-in speed to improve the starting performance. The biomimetic concept did not compromise the maximum power coefficient value of the turbine, being comparable to the device without the tubercles, but shifted the distribution of the coefficient over the range of the tip speed ratios tested