*Article* **Numerical Performance Model for Tensioned Mooring Tidal Turbine Operating in Combined Wave-Current Sea States**

**Song Fu \* and Cameron Johnstone**

Energy Systems Research Unit, Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow G1 1XQ, UK; cameron.johnstone@strath.ac.uk

**\*** Correspondence: song.fu@strath.ac.uk

**Abstract:** This study proposes the design of a tidal turbine station keeping system based on the adoption of a tensioned mooring system. Damping is introduced to investigate its effect on the reduction in the peak load experienced by tidal turbines during their operational lives in high-energy wave–current environments. A neutrally buoyant turbine is supported using a tensioned cable-based mooring system, where tension is introduced using a buoy fully submersed in water. The loads on the turbine rotor blades and buoy are calculated using a wave and current-coupled model. A modelling algorithm is proposed based on inverted pendulums, which respond to various sea state conditions, to study the behaviour of the system as well as the loads on blades. The results indicate that the tensioned mooring system reduces the peak thrust on the turbine and validates the applicability of the model.

**Keywords:** tidal turbine; modelling; mooring system; blade loading; wave–current interaction
