An investigation of tidal turbine performance and loads under various turbulence conditions using Blade Element Momentum theory and high-frequency field data acquired in two prospective tidal energy sites in Australia

Potential tidal energy sites are characterized by strong currents and high levels of shear, which is the main source of turbulent kinetic energy production. Enhanced turbulence levels are known to intensify fatigue loads acting on turbine blades, possibly causing premature device failure. Blade Element Momentum (BEM) numerical models allow for the investigation of device performance and loadings prior to device deployment and support turbine design optimization at low computational expenses. High-frequency novel Acoustic Doppler Current Profiler (AD2CP) data from two tidally energetic sites in Australia are used to feed a BEM model optimized to incorporate unsteady flow corrections. Power, thrust and bending moments coefficients as well as separation points are estimated to describe the performance of a turbine under various turbulence intensities and integral length scales. Results reveal that standard deviations were more sensitive than mean coefficients and turbulence in-tensities had a greater impact on performance coefficients than integral length scales. Periodic oscillations of separation points at two stations suggest the presence of weak dynamic stall but also that leading-edge vortex shedding is constrained to the blade roots. These findings highlight the need of assessing turbulence in tidal energy sites and support design improvements which can endure unsteady conditions.