WP1 results: CFD Modelling
Cavitation causes flow instabilities that hampers the functioning of flow devices, primarily by increasing the noise level, vibration, and, in extreme cases, the devices’ erosion.
Experimental tests have been carried out on two Magallanes tidal turbines. By tuning the turbines’ external pitch angle, we can achieve the “load-balancing” in terms of power output from both the turbines.
WP1 results: Cavitation testing
Optimizing the turbine geometry requires rigorous investigation of hydrodynamic behaviour of blades and their interaction with the supporting structure and nacelle. SSPA has performed experimental tests in order to provide a baseline for further improvement of the blade design by evaluating the performance of the model turbine and measuring the flow field using Laser Doppler Velocimetry (LDV) method.
WP1 results: Active control of hydrofoil cavitation testing
Tidal turbines play a crucial role in providing sustainable and pollution-free energy. In tidal turbines, cavitation is an important phenomena in determining the life span of the turbines.
NEMMO project partner Technion (Israel Institute of Technology) has developed and performed a high-order Large Eddy Simulations (LES) code, called MIRACLES, to study cavitation sheet dynamics associated with the modified scaled-down Francis turbine (hydrofoil) at angle of attack (AOA).
This research paper focuses on elucidating and analysing the re-entrant jet dynamics. Active cavitation control via steady wall jet injection was studied, but it had limited effect for the flow conditions (injection velocities and AOA) considered.
The results of this study are now available on the ScienceDirect: Interaction between surface blowing and re-entrant jet in active control of hydrofoil cavitation.
WP3 interim results: Materials & coatings
Developing novel materials and coatings for tidal turbine blades is one of the main objectives of the NEMMO project.
Three parallel approaches have been used to enhance blade material performances in order to increase their ageing, fouling, impact, and cavitation resistance:
- Improving the fatigue and impact resistance of the new nano-enhanced composite materials.
- Controlling biofouling by means of blade surface micro-texturing.
- Developing novel non-leaching anti-fouling coatings with permanent cavitation resistance through the design and synthesis of polymers bearing different functionalities within its chemical backbone and the incorporation of functionalized nanoparticles into such polymer formulations.
WP3 interim results: Surface textures
Part of the NEMMO project has been dedicated to designing an effective texture tailored to the NEMMO turbine. Bio-inspired surface modification has shown potential as an antifouling strategy. The surface textures can act on the ability of fouling micro-organisms to find secure attachment to the substrate but also alters fluid induced stresses over the organisms. The two effects combine to reduce initial settlement and improve the self-cleaning properties of the surface by altering cell adhesion in turbulent flows.