An investigation on compliant coating for tidal turbine blades

Hydrodynamic performances are critical for the energy efficiency of most marine industries. A drag reduction for ship hulls would contribute to the urgent need of diminishing the unsustainable consumption of fossil fuel and emissions of carbon dioxide, which account for 3% of the global carbon emissions. The drag of tidal turbine blades is proportional to the power extractable from the tidal stream and, therefore, a drag reduction would increase the capacity factor of tidal turbines and decrease the cost of renewable energy. For a typical ship hull and tidal turbine blade, the viscous forces are small compared inertial forces (Re≈10^8), the flow fluctuations are large compared to the average flow speed (Tu ≈10%) and the friction drag significantly contributes to the total drag. Recent findings suggest that in these flow conditions compliant walls can allow a friction drag reduction greater than 10%. Therefore, developing this flow control mechanism for the shipping and tidal energy industry can lead to a significant increase of energy efficiency. The use of compliant walls is extremely promising for a number of reasons: the potential drag reduction increases with the level of turbulence of the boundary layer; it has the additional effect of suppressing vibrations and flow-induced noise; it is a passive flow control means and therefore it is resilient to the hostile marine environment. The aim of the project is to provide proof of concept that well-designed compliant coatings can allow drag reduction and underpin future commercial exploitation for the shipping and tidal energy industry.