A validated BEM model to analyse hydrodynamic loading on tidal stream turbines blades

Abstract

This paper details a Blade Element Momentum (BEM) model for a 3 bladed, horizontal axis Tidal Stream Turbine (TST). The code capabilities are tested and validated by applying a range of different turbine parameters and operating conditions, where results are compared to numerous datasets. The model shows excellent agreement to performance and thrust measurements for 3 of the 4 datasets. Compared to other BEM models improved correlations are seen at higher rotational speeds. The fourth case shows over predictions of up to 30% in power at peak operating speed. In this case, CFD studies show better correlation due to the ability to capture detailed flow features around the blade as well as free surface effects, however require 3 to 4 orders of magnitude greater computational cost. Steady, non-uniform inflow functionality is incorporated into the model, where distributions of thrust and torque along the blade as well as cyclic loads are determined. These show the potential of the model to be used in combination with tools such as stress and fatigue analyses to improve the blade design process.