Performance and wake recovery of a tidal stream turbine under sheared inflow*

Tidal Stream Turbine (TST) deployed at tidal energy sites is subjected to asymmetrical effects like sheared flow, which will lead to non-uniform loadings and unsteady performance, thus affecting the device survivability. In our present study, we focus on the wake propagation of a 1:20 scale TST model in a sheared, turbulent inflow that is generated using an active grid turbulence generator in the Tidal Turbulence Test facility (T³F) housed at Lehigh University. The near-wake velocity fields are measured with an acoustic Doppler velocimeter at three tip speed ratios to provide comprehensive wake characterization at various operating conditions. Wake data is collected along the depthwise direction in the center-line of the test section up to a downstream location of 4D. Important wake flow statistics, such as wake deficit, turbulence intensity, isotropic ratio, swirl number, and energy recovery, will be estimated and compared with a baseline case, named quasi-laminar case, which has a homogeneous inflow profile with a comparatively low turbulence intensity (~2.2%).